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akaros / upstream / 4b1a7afbccf87e8c994220f903b6a29ce109a217 / . / kern / src / vfs.c
blob: 5005d387305254507a0edb7816d55f5e364843b9 [file] [log] [blame]
/* Copyright (c) 2009, 2010 The Regents of the University of California
* Barret Rhoden <brho@cs.berkeley.edu>
* See LICENSE for details.
*
* Default implementations and global values for the VFS. */
#include <vfs.h> // keep this first
#include <ros/errno.h>
#include <sys/queue.h>
#include <assert.h>
#include <stdio.h>
#include <atomic.h>
#include <slab.h>
#include <kmalloc.h>
#include <kfs.h>
#include <ext2fs.h>
#include <pmap.h>
#include <umem.h>
#include <smp.h>
#include <ns.h>
#include <fdtap.h>
struct sb_tailq super_blocks = TAILQ_HEAD_INITIALIZER(super_blocks);
spinlock_t super_blocks_lock = SPINLOCK_INITIALIZER;
struct fs_type_tailq file_systems = TAILQ_HEAD_INITIALIZER(file_systems);
struct namespace default_ns;
struct kmem_cache *dentry_kcache; // not to be confused with the dcache
struct kmem_cache *inode_kcache;
struct kmem_cache *file_kcache;
/* Mounts fs from dev_name at mnt_pt in namespace ns. There could be no mnt_pt,
* such as with the root of (the default) namespace. Not sure how it would work
* with multiple namespaces on the same FS yet. Note if you mount the same FS
* multiple times, you only have one FS still (and one SB). If we ever support
* that... */
struct vfsmount *__mount_fs(struct fs_type *fs, char *dev_name,
struct dentry *mnt_pt, int flags,
struct namespace *ns)
{
struct super_block *sb;
struct vfsmount *vmnt = kmalloc(sizeof(struct vfsmount), 0);
/* this first ref is stored in the NS tailq below */
kref_init(&vmnt->mnt_kref, fake_release, 1);
/* Build the vfsmount, if there is no mnt_pt, mnt is the root vfsmount (for
* now). fields related to the actual FS, like the sb and the mnt_root are
* set in the fs-specific get_sb() call. */
if (!mnt_pt) {
vmnt->mnt_parent = NULL;
vmnt->mnt_mountpoint = NULL;
} else { /* common case, but won't be tested til we try to mount another FS */
mnt_pt->d_mount_point = TRUE;
mnt_pt->d_mounted_fs = vmnt;
kref_get(&vmnt->mnt_kref, 1); /* held by mnt_pt */
vmnt->mnt_parent = mnt_pt->d_sb->s_mount;
vmnt->mnt_mountpoint = mnt_pt;
}
TAILQ_INIT(&vmnt->mnt_child_mounts);
vmnt->mnt_flags = flags;
vmnt->mnt_devname = dev_name;
vmnt->mnt_namespace = ns;
kref_get(&ns->kref, 1); /* held by vmnt */
/* Read in / create the SB */
sb = fs->get_sb(fs, flags, dev_name, vmnt);
if (!sb)
panic("You're FS sucks");
/* TODO: consider moving this into get_sb or something, in case the SB
* already exists (mounting again) (if we support that) */
spin_lock(&super_blocks_lock);
TAILQ_INSERT_TAIL(&super_blocks, sb, s_list); /* storing a ref here... */
spin_unlock(&super_blocks_lock);
/* Update holding NS */
spin_lock(&ns->lock);
TAILQ_INSERT_TAIL(&ns->vfsmounts, vmnt, mnt_list);
spin_unlock(&ns->lock);
/* note to self: so, right after this point, the NS points to the root FS
* mount (we return the mnt, which gets assigned), the root mnt has a dentry
* for /, backed by an inode, with a SB prepped and in memory. */
return vmnt;
}
void vfs_init(void)
{
struct fs_type *fs;
dentry_kcache = kmem_cache_create("dentry", sizeof(struct dentry),
__alignof__(struct dentry), 0, 0, 0);
inode_kcache = kmem_cache_create("inode", sizeof(struct inode),
__alignof__(struct inode), 0, 0, 0);
file_kcache = kmem_cache_create("file", sizeof(struct file),
__alignof__(struct file), 0, 0, 0);
/* default NS never dies, +1 to exist */
kref_init(&default_ns.kref, fake_release, 1);
spinlock_init(&default_ns.lock);
default_ns.root = NULL;
TAILQ_INIT(&default_ns.vfsmounts);
/* build list of all FS's in the system. put yours here. if this is ever
* done on the fly, we'll need to lock. */
TAILQ_INSERT_TAIL(&file_systems, &kfs_fs_type, list);
#ifdef CONFIG_EXT2FS
TAILQ_INSERT_TAIL(&file_systems, &ext2_fs_type, list);
#endif
TAILQ_FOREACH(fs, &file_systems, list)
printk("Supports the %s Filesystem\n", fs->name);
/* mounting KFS at the root (/), pending root= parameters */
// TODO: linux creates a temp root_fs, then mounts the real root onto that
default_ns.root = __mount_fs(&kfs_fs_type, "RAM", NULL, 0, &default_ns);
printk("vfs_init() completed\n");
}
/* FS's can provide another, if they want */
int generic_dentry_hash(struct dentry *dentry, struct qstr *qstr)
{
unsigned long hash = 5381;
for (int i = 0; i < qstr->len; i++) {
/* hash * 33 + c, djb2's technique */
hash = ((hash << 5) + hash) + qstr->name[i];
}
return hash;
}
/* Builds / populates the qstr of a dentry based on its d_iname. If there is an
* l_name, (long), it will use that instead of the inline name. This will
* probably change a bit. */
void qstr_builder(struct dentry *dentry, char *l_name)
{
dentry->d_name.name = l_name ? l_name : dentry->d_iname;
dentry->d_name.len = strnlen(dentry->d_name.name, MAX_FILENAME_SZ);
dentry->d_name.hash = dentry->d_op->d_hash(dentry, &dentry->d_name);
}
/* Useful little helper - return the string ptr for a given file */
char *file_name(struct file *file)
{
return file->f_dentry->d_name.name;
}
static int prepend(char **pbuf, size_t *pbuflen, const char *str, size_t len)
{
if (*pbuflen < len)
return -ENAMETOOLONG;
*pbuflen -= len;
*pbuf -= len;
memcpy(*pbuf, str, len);
return 0;
}
char *dentry_path(struct dentry *dentry, char *path, size_t max_size)
{
size_t csize = max_size;
char *path_start = path + max_size, *base;
if (prepend(&path_start, &csize, "\0", 1) < 0 || csize < 1)
return NULL;
/* Handle the case that the passed dentry is the root. */
base = path_start - 1;
*base = '/';
while (!DENTRY_IS_ROOT(dentry)) {
if (prepend(&path_start, &csize, dentry->d_name.name,
dentry->d_name.len) < 0 ||
prepend(&path_start, &csize, "/", 1) < 0)
return NULL;
base = path_start;
dentry = dentry->d_parent;
}
return base;
}
/* Some issues with this, coupled closely to fs_lookup.
*
* Note the use of __dentry_free, instead of kref_put. In those cases, we don't
* want to treat it like a kref and we have the only reference to it, so it is
* okay to do this. It makes dentry_release() easier too. */
static struct dentry *do_lookup(struct dentry *parent, char *name)
{
struct dentry *result, *query;
query = get_dentry(parent->d_sb, parent, name);
if (!query) {
warn("OOM in do_lookup(), probably wasn't expected\n");
return 0;
}
result = dcache_get(parent->d_sb, query);
if (result) {
__dentry_free(query);
return result;
}
/* No result, check for negative */
if (query->d_flags & DENTRY_NEGATIVE) {
__dentry_free(query);
return 0;
}
/* not in the dcache at all, need to consult the FS */
result = parent->d_inode->i_op->lookup(parent->d_inode, query, 0);
if (!result) {
/* Note the USED flag will get turned off when this gets added to the
* LRU in dentry_release(). There's a slight race here that we'll panic
* on, but I want to catch it (in dcache_put()) for now. */
query->d_flags |= DENTRY_NEGATIVE;
dcache_put(parent->d_sb, query);
kref_put(&query->d_kref);
return 0;
}
dcache_put(parent->d_sb, result);
/* This is because KFS doesn't return the same dentry, but ext2 does. this
* is ugly and needs to be fixed. (TODO) */
if (result != query)
__dentry_free(query);
/* TODO: if the following are done by us, how do we know the i_ino?
* also need to handle inodes that are already read in! For now, we're
* going to have the FS handle it in its lookup() method:
* - get a new inode
* - read in the inode
* - put in the inode cache */
return result;
}
/* Update ND such that it represents having followed dentry. IAW the nd
* refcnting rules, we need to decref any references that were in there before
* they get clobbered. */
static int next_link(struct dentry *dentry, struct nameidata *nd)
{
assert(nd->dentry && nd->mnt);
/* update the dentry */
kref_get(&dentry->d_kref, 1);
kref_put(&nd->dentry->d_kref);
nd->dentry = dentry;
/* update the mount, if we need to */
if (dentry->d_sb->s_mount != nd->mnt) {
kref_get(&dentry->d_sb->s_mount->mnt_kref, 1);
kref_put(&nd->mnt->mnt_kref);
nd->mnt = dentry->d_sb->s_mount;
}
return 0;
}
/* Walk up one directory, being careful of mountpoints, namespaces, and the top
* of the FS */
static int climb_up(struct nameidata *nd)
{
printd("CLIMB_UP, from %s\n", nd->dentry->d_name.name);
/* Top of the world, just return. Should also check for being at the top of
* the current process's namespace (TODO) */
if (!nd->dentry->d_parent || (nd->dentry->d_parent == nd->dentry))
return -1;
/* Check if we are at the top of a mount, if so, we need to follow
* backwards, and then climb_up from that one. We might need to climb
* multiple times if we mount multiple FSs at the same spot (highly
* unlikely). This is completely untested. Might recurse instead. */
while (nd->mnt->mnt_root == nd->dentry) {
if (!nd->mnt->mnt_parent) {
warn("Might have expected a parent vfsmount (dentry had a parent)");
return -1;
}
next_link(nd->mnt->mnt_mountpoint, nd);
}
/* Backwards walk (no mounts or any other issues now). */
next_link(nd->dentry->d_parent, nd);
printd("CLIMB_UP, to %s\n", nd->dentry->d_name.name);
return 0;
}
/* nd->dentry might be on a mount point, so we need to move on to the child
* mount's root. */
static int follow_mount(struct nameidata *nd)
{
if (!nd->dentry->d_mount_point)
return 0;
next_link(nd->dentry->d_mounted_fs->mnt_root, nd);
return 0;
}
static int link_path_walk(char *path, struct nameidata *nd);
/* When nd->dentry is for a symlink, this will recurse and follow that symlink,
* so that nd contains the results of following the symlink (dentry and mnt).
* Returns when it isn't a symlink, 1 on following a link, and < 0 on error. */
static int follow_symlink(struct nameidata *nd)
{
int retval;
char *symname;
if (!S_ISLNK(nd->dentry->d_inode->i_mode))
return 0;
if (nd->depth > MAX_SYMLINK_DEPTH)
return -ELOOP;
printd("Following symlink for dentry %p %s\n", nd->dentry,
nd->dentry->d_name.name);
nd->depth++;
symname = nd->dentry->d_inode->i_op->readlink(nd->dentry);
/* We need to pin in nd->dentry (the dentry of the symlink), since we need
* its symname's storage to stay in memory throughout the upcoming
* link_path_walk(). The last_sym gets decreffed when we path_release() or
* follow another symlink. */
if (nd->last_sym)
kref_put(&nd->last_sym->d_kref);
kref_get(&nd->dentry->d_kref, 1);
nd->last_sym = nd->dentry;
/* If this an absolute path in the symlink, we need to free the old path and
* start over, otherwise, we continue from the PARENT of nd (the symlink) */
if (symname[0] == '/') {
path_release(nd);
if (!current)
nd->dentry = default_ns.root->mnt_root;
else
nd->dentry = current->fs_env.root;
nd->mnt = nd->dentry->d_sb->s_mount;
kref_get(&nd->mnt->mnt_kref, 1);
kref_get(&nd->dentry->d_kref, 1);
} else {
climb_up(nd);
}
/* either way, keep on walking in the free world! */
retval = link_path_walk(symname, nd);
return (retval == 0 ? 1 : retval);
}
/* Little helper, to make it easier to break out of the nested loops. Will also
* '\0' out the first slash if it's slashes all the way down. Or turtles. */
static bool packed_trailing_slashes(char *first_slash)
{
for (char *i = first_slash; *i == '/'; i++) {
if (*(i + 1) == '\0') {
*first_slash = '\0';
return TRUE;
}
}
return FALSE;
}
/* Simple helper to set nd to track its last name to be Name. Also be careful
* with the storage of name. Don't use and nd's name past the lifetime of the
* string used in the path_lookup()/link_path_walk/whatever. Consider replacing
* parts of this with a qstr builder. Note this uses the dentry's d_op, which
* might not be the dentry we care about. */
static void stash_nd_name(struct nameidata *nd, char *name)
{
nd->last.name = name;
nd->last.len = strlen(name);
nd->last.hash = nd->dentry->d_op->d_hash(nd->dentry, &nd->last);
}
/* Resolves the links in a basic path walk. 0 for success, -EWHATEVER
* otherwise. The final lookup is returned via nd. */
static int link_path_walk(char *path, struct nameidata *nd)
{
struct dentry *link_dentry;
struct inode *link_inode, *nd_inode;
char *next_slash;
char *link = path;
int error;
/* Prevent crazy recursion */
if (nd->depth > MAX_SYMLINK_DEPTH)
return -ELOOP;
/* skip all leading /'s */
while (*link == '/')
link++;
/* if there's nothing left (null terminated), we're done. This should only
* happen for "/", which if we wanted a PARENT, should fail (there is no
* parent). */
if (*link == '\0') {
if (nd->flags & LOOKUP_PARENT) {
set_errno(ENOENT);
return -1;
}
/* o/w, we're good */
return 0;
}
/* iterate through each intermediate link of the path. in general, nd
* tracks where we are in the path, as far as dentries go. once we have the
* next dentry, we try to update nd based on that dentry. link is the part
* of the path string that we are looking up */
while (1) {
nd_inode = nd->dentry->d_inode;
if ((error = check_perms(nd_inode, nd->intent)))
return error;
/* find the next link, break out if it is the end */
next_slash = strchr(link, '/');
if (!next_slash) {
break;
} else {
if (packed_trailing_slashes(next_slash)) {
nd->flags |= LOOKUP_DIRECTORY;
break;
}
}
/* skip over any interim ./ */
if (!strncmp("./", link, 2))
goto next_loop;
/* Check for "../", walk up */
if (!strncmp("../", link, 3)) {
climb_up(nd);
goto next_loop;
}
*next_slash = '\0';
link_dentry = do_lookup(nd->dentry, link);
*next_slash = '/';
if (!link_dentry)
return -ENOENT;
/* make link_dentry the current step/answer */
next_link(link_dentry, nd);
kref_put(&link_dentry->d_kref); /* do_lookup gave us a refcnt dentry */
/* we could be on a mountpoint or a symlink - need to follow them */
follow_mount(nd);
if ((error = follow_symlink(nd)) < 0)
return error;
/* Turn off a possible DIRECTORY lookup, which could have been set
* during the follow_symlink (a symlink could have had a directory at
* the end), though it was in the middle of the real path. */
nd->flags &= ~LOOKUP_DIRECTORY;
if (!S_ISDIR(nd->dentry->d_inode->i_mode))
return -ENOTDIR;
next_loop:
/* move through the path string to the next entry */
link = next_slash + 1;
/* advance past any other interim slashes. we know we won't hit the end
* due to the for loop check above */
while (*link == '/')
link++;
}
/* Now, we're on the last link of the path. We need to deal with with . and
* .. . This might be weird with PARENT lookups - not sure what semantics
* we want exactly. This will give the parent of whatever the PATH was
* supposed to look like. Note that ND currently points to the parent of
* the last item (link). */
if (!strcmp(".", link)) {
if (nd->flags & LOOKUP_PARENT) {
assert(nd->dentry->d_name.name);
stash_nd_name(nd, nd->dentry->d_name.name);
climb_up(nd);
}
return 0;
}
if (!strcmp("..", link)) {
climb_up(nd);
if (nd->flags & LOOKUP_PARENT) {
assert(nd->dentry->d_name.name);
stash_nd_name(nd, nd->dentry->d_name.name);
climb_up(nd);
}
return 0;
}
/* need to attempt to look it up, in case it's a symlink */
link_dentry = do_lookup(nd->dentry, link);
if (!link_dentry) {
/* if there's no dentry, we are okay if we are looking for the parent */
if (nd->flags & LOOKUP_PARENT) {
assert(strcmp(link, ""));
stash_nd_name(nd, link);
return 0;
} else {
return -ENOENT;
}
}
next_link(link_dentry, nd);
kref_put(&link_dentry->d_kref); /* do_lookup gave us a refcnt'd dentry */
/* at this point, nd is on the final link, but it might be a symlink */
if (nd->flags & LOOKUP_FOLLOW) {
error = follow_symlink(nd);
if (error < 0)
return error;
/* if we actually followed a symlink, then nd is set and we're done */
if (error > 0)
return 0;
}
/* One way or another, nd is on the last element of the path, symlinks and
* all. Now we need to climb up to set nd back on the parent, if that's
* what we wanted */
if (nd->flags & LOOKUP_PARENT) {
assert(nd->dentry->d_name.name);
stash_nd_name(nd, link_dentry->d_name.name);
climb_up(nd);
return 0;
}
/* now, we have the dentry set, and don't want the parent, but might be on a
* mountpoint still. FYI: this hasn't been thought through completely. */
follow_mount(nd);
/* If we wanted a directory, but didn't get one, error out */
if ((nd->flags & LOOKUP_DIRECTORY) && !S_ISDIR(nd->dentry->d_inode->i_mode))
return -ENOTDIR;
return 0;
}
/* Given path, return the inode for the final dentry. The ND should be
* initialized for the first call - specifically, we need the intent.
* LOOKUP_PARENT and friends go in the flags var, which is not the intent.
*
* If path_lookup wants a PARENT, but hits the top of the FS (root or
* otherwise), we want it to error out. It's still unclear how we want to
* handle processes with roots that aren't root, but at the very least, we don't
* want to think we have the parent of /, but have / itself. Due to the way
* link_path_walk works, if that happened, we probably don't have a
* nd->last.name. This needs more thought (TODO).
*
* Need to be careful too. While the path has been copied-in to the kernel,
* it's still user input. */
int path_lookup(char *path, int flags, struct nameidata *nd)
{
int retval;
printd("Path lookup for %s\n", path);
/* we allow absolute lookups with no process context */
/* TODO: RCU read lock on pwd or kref_not_zero in a loop. concurrent chdir
* could decref nd->dentry before we get to incref it below. */
if (path[0] == '/') { /* absolute lookup */
if (!current)
nd->dentry = default_ns.root->mnt_root;
else
nd->dentry = current->fs_env.root;
} else { /* relative lookup */
assert(current);
/* Don't need to lock on the fs_env since we're reading one item */
nd->dentry = current->fs_env.pwd;
}
nd->mnt = nd->dentry->d_sb->s_mount;
/* Whenever references get put in the nd, incref them. Whenever they are
* removed, decref them. */
kref_get(&nd->mnt->mnt_kref, 1);
kref_get(&nd->dentry->d_kref, 1);
nd->flags = flags;
nd->depth = 0; /* used in symlink following */
retval = link_path_walk(path, nd);
/* make sure our PARENT lookup worked */
if (!retval && (flags & LOOKUP_PARENT))
assert(nd->last.name);
return retval;
}
/* Call this after any use of path_lookup when you are done with its results,
* regardless of whether it succeeded or not. It will free any references */
void path_release(struct nameidata *nd)
{
kref_put(&nd->dentry->d_kref);
kref_put(&nd->mnt->mnt_kref);
/* Free the last symlink dentry used, if there was one */
if (nd->last_sym) {
kref_put(&nd->last_sym->d_kref);
nd->last_sym = 0; /* catch reuse bugs */
}
}
/* External version of mount, only call this after having a / mount */
int mount_fs(struct fs_type *fs, char *dev_name, char *path, int flags)
{
struct nameidata nd_r = {0}, *nd = &nd_r;
int retval = 0;
retval = path_lookup(path, LOOKUP_DIRECTORY, nd);
if (retval)
goto out;
/* taking the namespace of the vfsmount of path */
if (!__mount_fs(fs, dev_name, nd->dentry, flags, nd->mnt->mnt_namespace))
retval = -EINVAL;
out:
path_release(nd);
return retval;
}
/* Superblock functions */
/* Dentry "hash" function for the hash table to use. Since we already have the
* hash in the qstr, we don't need to rehash. Also, note we'll be using the
* dentry in question as both the key and the value. */
static size_t __dcache_hash(void *k)
{
return (size_t)((struct dentry*)k)->d_name.hash;
}
/* Dentry cache hashtable equality function. This means we need to pass in some
* minimal dentry when doing a lookup. */
static ssize_t __dcache_eq(void *k1, void *k2)
{
if (((struct dentry*)k1)->d_parent != ((struct dentry*)k2)->d_parent)
return 0;
/* TODO: use the FS-specific string comparison */
return !strcmp(((struct dentry*)k1)->d_name.name,
((struct dentry*)k2)->d_name.name);
}
/* Helper to alloc and initialize a generic superblock. This handles all the
* VFS related things, like lists. Each FS will need to handle its own things
* in its *_get_sb(), usually involving reading off the disc. */
struct super_block *get_sb(void)
{
struct super_block *sb = kmalloc(sizeof(struct super_block), 0);
sb->s_dirty = FALSE;
spinlock_init(&sb->s_lock);
kref_init(&sb->s_kref, fake_release, 1); /* for the ref passed out */
TAILQ_INIT(&sb->s_inodes);
TAILQ_INIT(&sb->s_dirty_i);
TAILQ_INIT(&sb->s_io_wb);
TAILQ_INIT(&sb->s_lru_d);
TAILQ_INIT(&sb->s_files);
sb->s_dcache = create_hashtable(100, __dcache_hash, __dcache_eq);
sb->s_icache = create_hashtable(100, __generic_hash, __generic_eq);
spinlock_init(&sb->s_lru_lock);
spinlock_init(&sb->s_dcache_lock);
spinlock_init(&sb->s_icache_lock);
sb->s_fs_info = 0; // can override somewhere else
return sb;
}
/* Final stages of initializing a super block, including creating and linking
* the root dentry, root inode, vmnt, and sb. The d_op and root_ino are
* FS-specific, but otherwise its FS-independent, tricky, and not worth having
* around multiple times.
*
* Not the world's best interface, so it's subject to change, esp since we're
* passing (now 3) FS-specific things. */
void init_sb(struct super_block *sb, struct vfsmount *vmnt,
struct dentry_operations *d_op, unsigned long root_ino,
void *d_fs_info)
{
/* Build and init the first dentry / inode. The dentry ref is stored later
* by vfsmount's mnt_root. The parent is dealt with later. */
struct dentry *d_root = get_dentry_with_ops(sb, 0, "/", d_op);
if (!d_root)
panic("OOM! init_sb() can't fail yet!");
/* a lot of here on down is normally done in lookup() or create, since
* get_dentry isn't a fully usable dentry. The two FS-specific settings are
* normally inherited from a parent within the same FS in get_dentry, but we
* have none here. */
d_root->d_op = d_op;
d_root->d_fs_info = d_fs_info;
struct inode *inode = get_inode(d_root);
if (!inode)
panic("This FS sucks!");
inode->i_ino = root_ino;
/* TODO: add the inode to the appropriate list (off i_list) */
/* TODO: do we need to read in the inode? can we do this on demand? */
/* if this FS is already mounted, we'll need to do something different. */
sb->s_op->read_inode(inode);
icache_put(sb, inode);
/* Link the dentry and SB to the VFS mount */
vmnt->mnt_root = d_root; /* ref comes from get_dentry */
vmnt->mnt_sb = sb;
/* If there is no mount point, there is no parent. This is true only for
* the rootfs. */
if (vmnt->mnt_mountpoint) {
kref_get(&vmnt->mnt_mountpoint->d_kref, 1); /* held by d_root */
d_root->d_parent = vmnt->mnt_mountpoint; /* dentry of the root */
} else {
d_root->d_parent = d_root; /* set root as its own parent */
}
/* insert the dentry into the dentry cache. when's the earliest we can?
* when's the earliest we should? what about concurrent accesses to the
* same dentry? should be locking the dentry... */
dcache_put(sb, d_root);
kref_put(&inode->i_kref); /* give up the ref from get_inode() */
}
/* Dentry Functions */
static void dentry_set_name(struct dentry *dentry, char *name)
{
size_t name_len = strnlen(name, MAX_FILENAME_SZ); /* not including \0! */
char *l_name = 0;
if (name_len < DNAME_INLINE_LEN) {
strlcpy(dentry->d_iname, name, name_len + 1);
qstr_builder(dentry, 0);
} else {
l_name = kmalloc(name_len + 1, 0);
assert(l_name);
strlcpy(l_name, name, name_len + 1);
qstr_builder(dentry, l_name);
}
}
/* Gets a dentry. If there is no parent, use d_op. Only called directly by
* superblock init code. */
struct dentry *get_dentry_with_ops(struct super_block *sb,
struct dentry *parent, char *name,
struct dentry_operations *d_op)
{
assert(name);
struct dentry *dentry = kmem_cache_alloc(dentry_kcache, 0);
if (!dentry) {
set_errno(ENOMEM);
return 0;
}
//memset(dentry, 0, sizeof(struct dentry));
kref_init(&dentry->d_kref, dentry_release, 1); /* this ref is returned */
spinlock_init(&dentry->d_lock);
TAILQ_INIT(&dentry->d_subdirs);
dentry->d_time = 0;
kref_get(&sb->s_kref, 1);
dentry->d_sb = sb; /* storing a ref here... */
dentry->d_mount_point = FALSE;
dentry->d_mounted_fs = 0;
if (parent) { /* no parent for rootfs mount */
kref_get(&parent->d_kref, 1);
dentry->d_op = parent->d_op; /* d_op set in init_sb for parentless */
} else {
dentry->d_op = d_op;
}
dentry->d_parent = parent;
dentry->d_flags = DENTRY_USED;
dentry->d_fs_info = 0;
dentry_set_name(dentry, name);
/* Catch bugs by aggressively zeroing this (o/w we use old stuff) */
dentry->d_inode = 0;
return dentry;
}
/* Helper to alloc and initialize a generic dentry. The following needs to be
* set still: d_op (if no parent), d_fs_info (opt), d_inode, connect the inode
* to the dentry (and up the d_kref again), maybe dcache_put(). The inode
* stitching is done in get_inode() or lookup (depending on the FS).
* The setting of the d_op might be problematic when dealing with mounts. Just
* overwrite it.
*
* If the name is longer than the inline name, it will kmalloc a buffer, so
* don't worry about the storage for *name after calling this. */
struct dentry *get_dentry(struct super_block *sb, struct dentry *parent,
char *name)
{
return get_dentry_with_ops(sb, parent, name, 0);
}
/* Called when the dentry is unreferenced (after kref == 0). This works closely
* with the resurrection in dcache_get().
*
* The dentry is still in the dcache, but needs to be un-USED and added to the
* LRU dentry list. Even dentries that were used in a failed lookup need to be
* cached - they ought to be the negative dentries. Note that all dentries have
* parents, even negative ones (it is needed to find it in the dcache). */
void dentry_release(struct kref *kref)
{
struct dentry *dentry = container_of(kref, struct dentry, d_kref);
printd("'Releasing' dentry %p: %s\n", dentry, dentry->d_name.name);
/* DYING dentries (recently unlinked / rmdir'd) just get freed */
if (dentry->d_flags & DENTRY_DYING) {
__dentry_free(dentry);
return;
}
/* This lock ensures the USED state and the TAILQ membership is in sync.
* Also used to check the refcnt, though that might not be necessary. */
spin_lock(&dentry->d_lock);
/* While locked, we need to double check the kref, in case someone already
* reup'd it. Re-up? you're crazy! Reee-up, you're outta yo mind! */
if (!kref_refcnt(&dentry->d_kref)) {
/* Note this is where negative dentries get set UNUSED */
if (dentry->d_flags & DENTRY_USED) {
dentry->d_flags &= ~DENTRY_USED;
spin_lock(&dentry->d_sb->s_lru_lock);
TAILQ_INSERT_TAIL(&dentry->d_sb->s_lru_d, dentry, d_lru);
spin_unlock(&dentry->d_sb->s_lru_lock);
} else {
/* and make sure it wasn't USED, then UNUSED again */
/* TODO: think about issues with this */
warn("This should be rare. Tell brho this happened.");
}
}
spin_unlock(&dentry->d_lock);
}
/* Called when we really dealloc and get rid of a dentry (like when it is
* removed from the dcache, either for memory or correctness reasons)
*
* This has to handle two types of dentries: full ones (ones that had been used)
* and ones that had been just for lookups - hence the check for d_inode.
*
* Note that dentries pin and kref their inodes. When all the dentries are
* gone, we want the inode to be released via kref. The inode has internal /
* weak references to the dentry, which are not refcounted. */
void __dentry_free(struct dentry *dentry)
{
if (dentry->d_inode)
printd("Freeing dentry %p: %s\n", dentry, dentry->d_name.name);
assert(dentry->d_op); /* catch bugs. a while back, some lacked d_op */
dentry->d_op->d_release(dentry);
/* TODO: check/test the boundaries on this. */
if (dentry->d_name.len > DNAME_INLINE_LEN)
kfree((void*)dentry->d_name.name);
kref_put(&dentry->d_sb->s_kref);
if (dentry->d_parent)
kref_put(&dentry->d_parent->d_kref);
if (dentry->d_mounted_fs)
kref_put(&dentry->d_mounted_fs->mnt_kref);
if (dentry->d_inode) {
TAILQ_REMOVE(&dentry->d_inode->i_dentry, dentry, d_alias);
kref_put(&dentry->d_inode->i_kref); /* dentries kref inodes */
}
kmem_cache_free(dentry_kcache, dentry);
}
/* Looks up the dentry for the given path, returning a refcnt'd dentry (or 0).
* Permissions are applied for the current user, which is quite a broken system
* at the moment. Flags are lookup flags. */
struct dentry *lookup_dentry(char *path, int flags)
{
struct dentry *dentry;
struct nameidata nd_r = {0}, *nd = &nd_r;
int error;
error = path_lookup(path, flags, nd);
if (error) {
path_release(nd);
set_errno(-error);
return 0;
}
dentry = nd->dentry;
kref_get(&dentry->d_kref, 1);
path_release(nd);
return dentry;
}
/* Get a dentry from the dcache. At a minimum, we need the name hash and parent
* in what_i_want, though most uses will probably be from a get_dentry() call.
* We pass in the SB in the off chance that we don't want to use a get'd dentry.
*
* The unusual variable name (instead of just "key" or something) is named after
* ex-SPC Castro's porn folder. Caller deals with the memory for what_i_want.
*
* If the dentry is negative, we don't return the actual result - instead, we
* set the negative flag in 'what i want'. The reason is we don't want to
* kref_get() and then immediately put (causing dentry_release()). This also
* means that dentry_release() should never get someone who wasn't USED (barring
* the race, which it handles). And we don't need to ever have a dentry set as
* USED and NEGATIVE (which is always wrong, but would be needed for a cleaner
* dentry_release()).
*
* This is where we do the "kref resurrection" - we are returning a kref'd
* object, even if it wasn't kref'd before. This means the dcache does NOT hold
* krefs (it is a weak/internal ref), but it is a source of kref generation. We
* sync up with the possible freeing of the dentry by locking the table. See
* Doc/kref for more info. */
struct dentry *dcache_get(struct super_block *sb, struct dentry *what_i_want)
{
struct dentry *found;
/* This lock protects the hash, as well as ensures the returned object
* doesn't get deleted/freed out from under us */
spin_lock(&sb->s_dcache_lock);
found = hashtable_search(sb->s_dcache, what_i_want);
if (found) {
if (found->d_flags & DENTRY_NEGATIVE) {
what_i_want->d_flags |= DENTRY_NEGATIVE;
spin_unlock(&sb->s_dcache_lock);
return 0;
}
spin_lock(&found->d_lock);
__kref_get(&found->d_kref, 1); /* prob could be done outside the lock*/
/* If we're here (after kreffing) and it is not USED, we are the one who
* should resurrect */
if (!(found->d_flags & DENTRY_USED)) {
found->d_flags |= DENTRY_USED;
spin_lock(&sb->s_lru_lock);
TAILQ_REMOVE(&sb->s_lru_d, found, d_lru);
spin_unlock(&sb->s_lru_lock);
}
spin_unlock(&found->d_lock);
}
spin_unlock(&sb->s_dcache_lock);
return found;
}
/* Adds a dentry to the dcache. Note the *dentry is both the key and the value.
* If the value was already in there (which can happen iff it was negative), for
* now we'll remove it and put the new one in there. */
void dcache_put(struct super_block *sb, struct dentry *key_val)
{
struct dentry *old;
int retval;
spin_lock(&sb->s_dcache_lock);
old = hashtable_remove(sb->s_dcache, key_val);
/* if it is old and non-negative, our caller lost a race with someone else
* adding the dentry. but since we yanked it out, like a bunch of idiots,
* we still have to put it back. should be fairly rare. */
if (old && (old->d_flags & DENTRY_NEGATIVE)) {
/* This is possible, but rare for now (about to be put on the LRU) */
assert(!(old->d_flags & DENTRY_USED));
assert(!kref_refcnt(&old->d_kref));
spin_lock(&sb->s_lru_lock);
TAILQ_REMOVE(&sb->s_lru_d, old, d_lru);
spin_unlock(&sb->s_lru_lock);
/* TODO: this seems suspect. isn't this the same memory as key_val?
* in which case, we just adjust the flags (remove NEG) and reinsert? */
assert(old != key_val); // checking TODO comment
__dentry_free(old);
}
/* this returns 0 on failure (TODO: Fix this ghetto shit) */
retval = hashtable_insert(sb->s_dcache, key_val, key_val);
assert(retval);
spin_unlock(&sb->s_dcache_lock);
}
/* Will remove and return the dentry. Caller deallocs the key, but the retval
* won't have a reference. * Returns 0 if it wasn't found. Callers can't
* assume much - they should not use the reference they *get back*, (if they
* already had one for key, they can use that). There may be other users out
* there. */
struct dentry *dcache_remove(struct super_block *sb, struct dentry *key)
{
struct dentry *retval;
spin_lock(&sb->s_dcache_lock);
retval = hashtable_remove(sb->s_dcache, key);
spin_unlock(&sb->s_dcache_lock);
return retval;
}
/* This will clean out the LRU list, which are the unused dentries of the dentry
* cache. This will optionally only free the negative ones. Note that we grab
* the hash lock for the time we traverse the LRU list - this prevents someone
* from getting a kref from the dcache, which could cause us trouble (we rip
* someone off the list, who isn't unused, and they try to rip them off the
* list). */
void dcache_prune(struct super_block *sb, bool negative_only)
{
struct dentry *d_i, *temp;
struct dentry_tailq victims = TAILQ_HEAD_INITIALIZER(victims);
spin_lock(&sb->s_dcache_lock);
spin_lock(&sb->s_lru_lock);
TAILQ_FOREACH_SAFE(d_i, &sb->s_lru_d, d_lru, temp) {
if (!(d_i->d_flags & DENTRY_USED)) {
if (negative_only && !(d_i->d_flags & DENTRY_NEGATIVE))
continue;
/* another place where we'd be better off with tools, not sol'ns */
hashtable_remove(sb->s_dcache, d_i);
TAILQ_REMOVE(&sb->s_lru_d, d_i, d_lru);
TAILQ_INSERT_HEAD(&victims, d_i, d_lru);
}
}
spin_unlock(&sb->s_lru_lock);
spin_unlock(&sb->s_dcache_lock);
/* Now do the actual freeing, outside of the hash/LRU list locks. This is
* necessary since __dentry_free() will decref its parent, which may get
* released and try to add itself to the LRU. */
TAILQ_FOREACH_SAFE(d_i, &victims, d_lru, temp) {
TAILQ_REMOVE(&victims, d_i, d_lru);
assert(!kref_refcnt(&d_i->d_kref));
__dentry_free(d_i);
}
/* It is possible at this point that there are new items on the LRU. We
* could loop back until that list is empty, if we care about this. */
}
/* Inode Functions */
/* Creates and initializes a new inode. Generic fields are filled in.
* FS-specific fields are filled in by the callout. Specific fields are filled
* in in read_inode() based on what's on the disk for a given i_no, or when the
* inode is created (for new objects).
*
* i_no is set by the caller. Note that this means this inode can be for an
* inode that is already on disk, or it can be used when creating. */
struct inode *get_inode(struct dentry *dentry)
{
struct super_block *sb = dentry->d_sb;
/* FS allocs and sets the following: i_op, i_fop, i_pm.pm_op, and any FS
* specific stuff. */
struct inode *inode = sb->s_op->alloc_inode(sb);
if (!inode) {
set_errno(ENOMEM);
return 0;
}
TAILQ_INSERT_HEAD(&sb->s_inodes, inode, i_sb_list); /* weak inode ref */
TAILQ_INIT(&inode->i_dentry);
TAILQ_INSERT_TAIL(&inode->i_dentry, dentry, d_alias); /* weak dentry ref*/
/* one for the dentry->d_inode, one passed out */
kref_init(&inode->i_kref, inode_release, 2);
dentry->d_inode = inode;
inode->i_ino = 0; /* set by caller later */
inode->i_blksize = sb->s_blocksize;
spinlock_init(&inode->i_lock);
kref_get(&sb->s_kref, 1); /* could allow the dentry to pin it */
inode->i_sb = sb;
inode->i_rdev = 0; /* this has no real meaning yet */
inode->i_bdev = sb->s_bdev; /* storing an uncounted ref */
inode->i_state = 0; /* need real states, like I_NEW */
inode->dirtied_when = 0;
inode->i_flags = 0;
atomic_set(&inode->i_writecount, 0);
/* Set up the page_map structures. Default is to use the embedded one.
* Might push some of this back into specific FSs. For now, the FS tells us
* what pm_op they want via i_pm.pm_op, which we set again in pm_init() */
inode->i_mapping = &inode->i_pm;
pm_init(inode->i_mapping, inode->i_pm.pm_op, inode);
return inode;
}
/* Helper: loads/ reads in the inode numbered ino and attaches it to dentry */
void load_inode(struct dentry *dentry, unsigned long ino)
{
struct inode *inode;
/* look it up in the inode cache first */
inode = icache_get(dentry->d_sb, ino);
if (inode) {
/* connect the dentry to its inode */
TAILQ_INSERT_TAIL(&inode->i_dentry, dentry, d_alias);
dentry->d_inode = inode; /* storing the ref we got from icache_get */
return;
}
/* otherwise, we need to do it manually */
inode = get_inode(dentry);
inode->i_ino = ino;
dentry->d_sb->s_op->read_inode(inode);
/* TODO: race here, two creators could miss in the cache, and then get here.
* need a way to sync across a blocking call. needs to be either at this
* point in the code or per the ino (dentries could be different) */
icache_put(dentry->d_sb, inode);
kref_put(&inode->i_kref);
}
/* Helper op, used when creating regular files, directories, symlinks, etc.
* Note we make a distinction between the mode and the file type (for now).
* After calling this, call the FS specific version (create or mkdir), which
* will set the i_ino, the filetype, and do any other FS-specific stuff. Also
* note that a lot of inode stuff was initialized in get_inode/alloc_inode. The
* stuff here is pertinent to the specific creator (user), mode, and time. Also
* note we don't pass this an nd, like Linux does... */
static struct inode *create_inode(struct dentry *dentry, int mode)
{
struct timespec now = nsec2timespec(epoch_nsec());
/* note it is the i_ino that uniquely identifies a file in the specific
* filesystem. there's a diff between creating an inode (even for an in-use
* ino) and then filling it in, and vs creating a brand new one.
* get_inode() sets it to 0, and it should be filled in later in an
* FS-specific manner. */
struct inode *inode = get_inode(dentry);
if (!inode)
return 0;
inode->i_mode = mode & S_PMASK; /* note that after this, we have no type */
inode->i_nlink = 1;
inode->i_size = 0;
inode->i_blocks = 0;
inode->i_atime.tv_sec = now.tv_sec;
inode->i_ctime.tv_sec = now.tv_sec;
inode->i_mtime.tv_sec = now.tv_sec;
inode->i_atime.tv_nsec = now.tv_nsec;
inode->i_ctime.tv_nsec = now.tv_nsec;
inode->i_mtime.tv_nsec = now.tv_nsec;
inode->i_bdev = inode->i_sb->s_bdev;
/* when we have notions of users, do something here: */
inode->i_uid = 0;
inode->i_gid = 0;
return inode;
}
/* Create a new disk inode in dir associated with dentry, with the given mode.
* called when creating a regular file. dir is the directory/parent. dentry is
* the dentry of the inode we are creating. Note the lack of the nd... */
int create_file(struct inode *dir, struct dentry *dentry, int mode)
{
struct inode *new_file = create_inode(dentry, mode);
if (!new_file)
return -1;
dir->i_op->create(dir, dentry, mode, 0);
icache_put(new_file->i_sb, new_file);
kref_put(&new_file->i_kref);
return 0;
}
/* Creates a new inode for a directory associated with dentry in dir with the
* given mode. */
int create_dir(struct inode *dir, struct dentry *dentry, int mode)
{
struct inode *new_dir = create_inode(dentry, mode);
if (!new_dir)
return -1;
dir->i_op->mkdir(dir, dentry, mode);
dir->i_nlink++; /* Directories get a hardlink for every child dir */
/* Make sure my parent tracks me. This is okay, since no directory (dir)
* can have more than one dentry */
struct dentry *parent = TAILQ_FIRST(&dir->i_dentry);
assert(parent && parent == TAILQ_LAST(&dir->i_dentry, dentry_tailq));
/* parent dentry tracks dentry as a subdir, weak reference */
TAILQ_INSERT_TAIL(&parent->d_subdirs, dentry, d_subdirs_link);
icache_put(new_dir->i_sb, new_dir);
kref_put(&new_dir->i_kref);
return 0;
}
/* Creates a new inode for a symlink associated with dentry in dir, containing
* the symlink symname */
int create_symlink(struct inode *dir, struct dentry *dentry,
const char *symname, int mode)
{
struct inode *new_sym = create_inode(dentry, mode);
if (!new_sym)
return -1;
dir->i_op->symlink(dir, dentry, symname);
icache_put(new_sym->i_sb, new_sym);
kref_put(&new_sym->i_kref);
return 0;
}
/* Returns 0 if the given mode is acceptable for the inode, and an appropriate
* error code if not. Needs to be writen, based on some sensible rules, and
* will also probably use 'current' */
int check_perms(struct inode *inode, int access_mode)
{
return 0; /* anything goes! */
}
/* Called after all external refs are gone to clean up the inode. Once this is
* called, all dentries pointing here are already done (one of them triggered
* this via kref_put(). */
void inode_release(struct kref *kref)
{
struct inode *inode = container_of(kref, struct inode, i_kref);
TAILQ_REMOVE(&inode->i_sb->s_inodes, inode, i_sb_list);
icache_remove(inode->i_sb, inode->i_ino);
/* Might need to write back or delete the file/inode */
if (inode->i_nlink) {
if (inode->i_state & I_STATE_DIRTY)
inode->i_sb->s_op->write_inode(inode, TRUE);
} else {
inode->i_sb->s_op->delete_inode(inode);
}
if (S_ISFIFO(inode->i_mode)) {
page_decref(kva2page(inode->i_pipe->p_buf));
kfree(inode->i_pipe);
}
/* TODO: (BDEV) */
// kref_put(inode->i_bdev->kref); /* assuming it's a bdev, could be a pipe*/
/* Either way, we dealloc the in-memory version */
inode->i_sb->s_op->dealloc_inode(inode); /* FS-specific clean-up */
kref_put(&inode->i_sb->s_kref);
/* TODO: clean this up */
assert(inode->i_mapping == &inode->i_pm);
kmem_cache_free(inode_kcache, inode);
}
/* Fills in kstat with the stat information for the inode */
void stat_inode(struct inode *inode, struct kstat *kstat)
{
kstat->st_dev = inode->i_sb->s_dev;
kstat->st_ino = inode->i_ino;
kstat->st_mode = inode->i_mode;
kstat->st_nlink = inode->i_nlink;
kstat->st_uid = inode->i_uid;
kstat->st_gid = inode->i_gid;
kstat->st_rdev = inode->i_rdev;
kstat->st_size = inode->i_size;
kstat->st_blksize = inode->i_blksize;
kstat->st_blocks = inode->i_blocks;
kstat->st_atim = inode->i_atime;
kstat->st_mtim = inode->i_mtime;
kstat->st_ctim = inode->i_ctime;
}
void print_kstat(struct kstat *kstat)
{
printk("kstat info for %p:\n", kstat);
printk("\tst_dev : %p\n", kstat->st_dev);
printk("\tst_ino : %p\n", kstat->st_ino);
printk("\tst_mode : %p\n", kstat->st_mode);
printk("\tst_nlink : %p\n", kstat->st_nlink);
printk("\tst_uid : %p\n", kstat->st_uid);
printk("\tst_gid : %p\n", kstat->st_gid);
printk("\tst_rdev : %p\n", kstat->st_rdev);
printk("\tst_size : %p\n", kstat->st_size);
printk("\tst_blksize: %p\n", kstat->st_blksize);
printk("\tst_blocks : %p\n", kstat->st_blocks);
printk("\tst_atime : %p\n", kstat->st_atim);
printk("\tst_mtime : %p\n", kstat->st_mtim);
printk("\tst_ctime : %p\n", kstat->st_ctim);
}
/* Inode Cache management. In general, search on the ino, get a refcnt'd value
* back. Remove does not give you a reference back - it should only be called
* in inode_release(). */
struct inode *icache_get(struct super_block *sb, unsigned long ino)
{
/* This is the same style as in pid2proc, it's the "safely create a strong
* reference from a weak one, so long as other strong ones exist" pattern */
spin_lock(&sb->s_icache_lock);
struct inode *inode = hashtable_search(sb->s_icache, (void*)ino);
if (inode)
if (!kref_get_not_zero(&inode->i_kref, 1))
inode = 0;
spin_unlock(&sb->s_icache_lock);
return inode;
}
void icache_put(struct super_block *sb, struct inode *inode)
{
spin_lock(&sb->s_icache_lock);
/* there's a race in load_ino() that could trigger this */
assert(!hashtable_search(sb->s_icache, (void*)inode->i_ino));
hashtable_insert(sb->s_icache, (void*)inode->i_ino, inode);
spin_unlock(&sb->s_icache_lock);
}
struct inode *icache_remove(struct super_block *sb, unsigned long ino)
{
struct inode *inode;
/* Presumably these hashtable removals could be easier since callers
* actually know who they are (same with the pid2proc hash) */
spin_lock(&sb->s_icache_lock);
inode = hashtable_remove(sb->s_icache, (void*)ino);
spin_unlock(&sb->s_icache_lock);
assert(inode && !kref_refcnt(&inode->i_kref));
return inode;
}
/* File functions */
/* Read count bytes from the file into buf, starting at *offset, which is
* increased accordingly, returning the number of bytes transfered. Most
* filesystems will use this function for their f_op->read.
* Note, this uses the page cache. */
ssize_t generic_file_read(struct file *file, char *buf, size_t count,
off64_t *offset)
{
struct page *page;
int error;
off64_t page_off;
unsigned long first_idx, last_idx;
size_t copy_amt;
char *buf_end;
/* read in offset, in case of a concurrent reader/writer, so we don't screw
* up our math for count, the idxs, etc. */
off64_t orig_off = ACCESS_ONCE(*offset);
/* Consider pushing some error checking higher in the VFS */
if (!count)
return 0;
if (!(file->f_flags & O_READ)) {
set_errno(EBADF);
return 0;
}
if (orig_off >= file->f_dentry->d_inode->i_size)
return 0; /* EOF */
/* Make sure we don't go past the end of the file */
if (orig_off + count > file->f_dentry->d_inode->i_size) {
count = file->f_dentry->d_inode->i_size - orig_off;
}
assert((long)count > 0);
page_off = orig_off & (PGSIZE - 1);
first_idx = orig_off >> PGSHIFT;
last_idx = (orig_off + count) >> PGSHIFT;
buf_end = buf + count;
/* For each file page, make sure it's in the page cache, then copy it out.
* TODO: will probably need to consider concurrently truncated files here.*/
for (int i = first_idx; i <= last_idx; i++) {
error = pm_load_page(file->f_mapping, i, &page);
assert(!error); /* TODO: handle ENOMEM and friends */
copy_amt = MIN(PGSIZE - page_off, buf_end - buf);
/* TODO: (KFOP) Probably shouldn't do this. Either memcpy directly, or
* split out the is_user_r(w)addr from copy_{to,from}_user() */
if (!is_ktask(per_cpu_info[core_id()].cur_kthread))
memcpy_to_user(current, buf, page2kva(page) + page_off, copy_amt);
else
memcpy(buf, page2kva(page) + page_off, copy_amt);
buf += copy_amt;
page_off = 0;
pm_put_page(page); /* it's still in the cache, we just don't need it */
}
assert(buf == buf_end);
/* could have concurrent file ops that screw with offset, so userspace isn't
* safe. but at least it'll be a value that one of the concurrent ops could
* have produced (compared to *offset_changed_concurrently += count. */
*offset = orig_off + count;
return count;
}
/* Write count bytes from buf to the file, starting at *offset, which is
* increased accordingly, returning the number of bytes transfered. Most
* filesystems will use this function for their f_op->write. Note, this uses
* the page cache.
*
* Changes don't get flushed to disc til there is an fsync, page cache eviction,
* or other means of trying to writeback the pages. */
ssize_t generic_file_write(struct file *file, const char *buf, size_t count,
off64_t *offset)
{
struct page *page;
int error;
off64_t page_off;
unsigned long first_idx, last_idx;
size_t copy_amt;
const char *buf_end;
off64_t orig_off = ACCESS_ONCE(*offset);
/* Consider pushing some error checking higher in the VFS */
if (!count)
return 0;
if (!(file->f_flags & O_WRITE)) {
set_errno(EBADF);
return 0;
}
if (file->f_flags & O_APPEND) {
spin_lock(&file->f_dentry->d_inode->i_lock);
orig_off = file->f_dentry->d_inode->i_size;
/* setting the filesize here, instead of during the extend-check, since
* we need to atomically reserve space and set our write position. */
file->f_dentry->d_inode->i_size += count;
spin_unlock(&file->f_dentry->d_inode->i_lock);
} else {
if (orig_off + count > file->f_dentry->d_inode->i_size) {
/* lock for writes to i_size. we allow lockless reads. recheck
* i_size in case of concurrent writers since our orig check. */
spin_lock(&file->f_dentry->d_inode->i_lock);
if (orig_off + count > file->f_dentry->d_inode->i_size)
file->f_dentry->d_inode->i_size = orig_off + count;
spin_unlock(&file->f_dentry->d_inode->i_lock);
}
}
page_off = orig_off & (PGSIZE - 1);
first_idx = orig_off >> PGSHIFT;
last_idx = (orig_off + count) >> PGSHIFT;
buf_end = buf + count;
/* For each file page, make sure it's in the page cache, then write it.*/
for (int i = first_idx; i <= last_idx; i++) {
error = pm_load_page(file->f_mapping, i, &page);
assert(!error); /* TODO: handle ENOMEM and friends */
copy_amt = MIN(PGSIZE - page_off, buf_end - buf);
/* TODO: (UMEM) (KFOP) think about this. */
if (!is_ktask(per_cpu_info[core_id()].cur_kthread))
memcpy_from_user(current, page2kva(page) + page_off, buf, copy_amt);
else
memcpy(page2kva(page) + page_off, buf, copy_amt);
buf += copy_amt;
page_off = 0;
atomic_or(&page->pg_flags, PG_DIRTY);
pm_put_page(page); /* it's still in the cache, we just don't need it */
}
assert(buf == buf_end);
*offset = orig_off + count;
return count;
}
/* Directories usually use this for their read method, which is the way glibc
* currently expects us to do a readdir (short of doing linux's getdents). Will
* probably need work, based on whatever real programs want. */
ssize_t generic_dir_read(struct file *file, char *u_buf, size_t count,
off64_t *offset)
{
struct kdirent dir_r = {0}, *dirent = &dir_r;
int retval = 1;
size_t amt_copied = 0;
char *buf_end = u_buf + count;
if (!S_ISDIR(file->f_dentry->d_inode->i_mode)) {
set_errno(ENOTDIR);
return -1;
}
if (!count)
return 0;
if (!(file->f_flags & O_READ)) {
set_errno(EBADF);
return 0;
}
/* start readdir from where it left off: */
dirent->d_off = *offset;
for ( ;
u_buf + sizeof(struct kdirent) <= buf_end;
u_buf += sizeof(struct kdirent)) {
/* TODO: UMEM/KFOP (pin the u_buf in the syscall, ditch the local copy,
* get rid of this memcpy and reliance on current, etc). Might be
* tricky with the dirent->d_off and trust issues */
retval = file->f_op->readdir(file, dirent);
if (retval < 0) {
set_errno(-retval);
break;
}
/* Slight info exposure: could be extra crap after the name in the
* dirent (like the name of a deleted file) */
if (!is_ktask(per_cpu_info[core_id()].cur_kthread))
memcpy_to_user(current, u_buf, dirent, sizeof(struct dirent));
else
memcpy(u_buf, dirent, sizeof(struct dirent));
amt_copied += sizeof(struct dirent);
/* 0 signals end of directory */
if (retval == 0)
break;
}
/* Next time read is called, we pick up where we left off */
*offset = dirent->d_off; /* UMEM */
/* important to tell them how much they got. they often keep going til they
* get 0 back (in the case of ls). It's also how much has been read, but it
* isn't how much the f_pos has moved (which is opaque to the VFS). */
return amt_copied;
}
/* Opens the file, using permissions from current for lack of a better option.
* It will attempt to create the file if it does not exist and O_CREAT is
* specified. This will return 0 on failure, and set errno. TODO: There's some
* stuff that we don't do, esp related file truncating/creation. flags are for
* opening, the mode is for creating. The flags related to how to create
* (O_CREAT_FLAGS) are handled in this function, not in create_file().
*
* It's tempting to split this into a do_file_create and a do_file_open, based
* on the O_CREAT flag, but the O_CREAT flag can be ignored if the file exists
* already and O_EXCL isn't specified. We could have open call create if it
* fails, but for now we'll keep it as is. */
struct file *do_file_open(char *path, int flags, int mode)
{
struct file *file = 0;
struct dentry *file_d;
struct inode *parent_i;
struct nameidata nd_r = {0}, *nd = &nd_r;
int error;
unsigned long nr_pages;
/* The file might exist, lets try to just open it right away */
nd->intent = LOOKUP_OPEN;
error = path_lookup(path, LOOKUP_FOLLOW, nd);
if (!error) {
if (S_ISDIR(nd->dentry->d_inode->i_mode) && (flags & O_WRITE)) {
set_errno(EISDIR);
goto out_path_only;
}
/* Also need to make sure we didn't want to O_EXCL create */
if ((flags & O_CREAT) && (flags & O_EXCL)) {
set_errno(EEXIST);
goto out_path_only;
}
file_d = nd->dentry;
kref_get(&file_d->d_kref, 1);
goto open_the_file;
}
if (!(flags & O_CREAT)) {
set_errno(-error);
goto out_path_only;
}
/* So it didn't already exist, release the path from the previous lookup,
* and then we try to create it. */
path_release(nd);
/* get the parent, following links. this means you get the parent of the
* final link (which may not be in 'path' in the first place. */
nd->intent = LOOKUP_CREATE;
error = path_lookup(path, LOOKUP_PARENT | LOOKUP_FOLLOW, nd);
if (error) {
set_errno(-error);
goto out_path_only;
}
/* see if the target is there (shouldn't be), and handle accordingly */
file_d = do_lookup(nd->dentry, nd->last.name);
if (!file_d) {
if (!(flags & O_CREAT)) {
warn("Extremely unlikely race, probably a bug");
set_errno(ENOENT);
goto out_path_only;
}
/* Create the inode/file. get a fresh dentry too: */
file_d = get_dentry(nd->dentry->d_sb, nd->dentry, nd->last.name);
if (!file_d)
goto out_path_only;
parent_i = nd->dentry->d_inode;
/* Note that the mode technically should only apply to future opens,
* but we apply it immediately. */
if (create_file(parent_i, file_d, mode)) /* sets errno */
goto out_file_d;
dcache_put(file_d->d_sb, file_d);
} else { /* something already exists */
/* this can happen due to concurrent access, but needs to be thought
* through */
panic("File shouldn't be here!");
if ((flags & O_CREAT) && (flags & O_EXCL)) {
/* wanted to create, not open, bail out */
set_errno(EEXIST);
goto out_file_d;
}
}
open_the_file:
/* now open the file (freshly created or if it already existed). At this
* point, file_d is a refcnt'd dentry, regardless of which branch we took.*/
if (flags & O_TRUNC) {
spin_lock(&file_d->d_inode->i_lock);
nr_pages = ROUNDUP(file_d->d_inode->i_size, PGSIZE) >> PGSHIFT;
file_d->d_inode->i_size = 0;
spin_unlock(&file_d->d_inode->i_lock);
pm_remove_contig(file_d->d_inode->i_mapping, 0, nr_pages);
}
file = dentry_open(file_d, flags); /* sets errno */
/* Note the fall through to the exit paths. File is 0 by default and if
* dentry_open fails. */
out_file_d:
kref_put(&file_d->d_kref);
out_path_only:
path_release(nd);
return file;
}
/* Path is the location of the symlink, sometimes called the "new path", and
* symname is who we link to, sometimes called the "old path". */
int do_symlink(char *path, const char *symname, int mode)
{
struct dentry *sym_d;
struct inode *parent_i;
struct nameidata nd_r = {0}, *nd = &nd_r;
int error;
int retval = -1;
nd->intent = LOOKUP_CREATE;
/* get the parent, but don't follow links */
error = path_lookup(path, LOOKUP_PARENT, nd);
if (error) {
set_errno(-error);
goto out_path_only;
}
/* see if the target is already there, handle accordingly */
sym_d = do_lookup(nd->dentry, nd->last.name);
if (sym_d) {
set_errno(EEXIST);
goto out_sym_d;
}
/* Doesn't already exist, let's try to make it: */
sym_d = get_dentry(nd->dentry->d_sb, nd->dentry, nd->last.name);
if (!sym_d)
goto out_path_only;
parent_i = nd->dentry->d_inode;
if (create_symlink(parent_i, sym_d, symname, mode))
goto out_sym_d;
dcache_put(sym_d->d_sb, sym_d);
retval = 0; /* Note the fall through to the exit paths */
out_sym_d:
kref_put(&sym_d->d_kref);
out_path_only:
path_release(nd);
return retval;
}
/* Makes a hard link for the file behind old_path to new_path */
int do_link(char *old_path, char *new_path)
{
struct dentry *link_d, *old_d;
struct inode *inode, *parent_dir;
struct nameidata nd_r = {0}, *nd = &nd_r;
int error;
int retval = -1;
nd->intent = LOOKUP_CREATE;
/* get the absolute parent of the new_path */
error = path_lookup(new_path, LOOKUP_PARENT | LOOKUP_FOLLOW, nd);
if (error) {
set_errno(-error);
goto out_path_only;
}
parent_dir = nd->dentry->d_inode;
/* see if the new target is already there, handle accordingly */
link_d = do_lookup(nd->dentry, nd->last.name);
if (link_d) {
set_errno(EEXIST);
goto out_link_d;
}
/* Doesn't already exist, let's try to make it. Still need to stitch it to
* an inode and set its FS-specific stuff after this.*/
link_d = get_dentry(nd->dentry->d_sb, nd->dentry, nd->last.name);
if (!link_d)
goto out_path_only;
/* Now let's get the old_path target */
old_d = lookup_dentry(old_path, LOOKUP_FOLLOW);
if (!old_d) /* errno set by lookup_dentry */
goto out_link_d;
/* For now, can only link to files */
if (!S_ISREG(old_d->d_inode->i_mode)) {
set_errno(EPERM);
goto out_both_ds;
}
/* Must be on the same FS */
if (old_d->d_sb != link_d->d_sb) {
set_errno(EXDEV);
goto out_both_ds;
}
/* Do whatever FS specific stuff there is first (which is also a chance to
* bail out). */
error = parent_dir->i_op->link(old_d, parent_dir, link_d);
if (error) {
set_errno(-error);
goto out_both_ds;
}
/* Finally stitch it up */
inode = old_d->d_inode;
kref_get(&inode->i_kref, 1);
link_d->d_inode = inode;
inode->i_nlink++;
TAILQ_INSERT_TAIL(&inode->i_dentry, link_d, d_alias); /* weak ref */
dcache_put(link_d->d_sb, link_d);
retval = 0; /* Note the fall through to the exit paths */
out_both_ds:
kref_put(&old_d->d_kref);
out_link_d:
kref_put(&link_d->d_kref);
out_path_only:
path_release(nd);
return retval;
}
/* Unlinks path from the directory tree. Read the Documentation for more info.
*/
int do_unlink(char *path)
{
struct dentry *dentry;
struct inode *parent_dir;
struct nameidata nd_r = {0}, *nd = &nd_r;
int error;
int retval = -1;
/* get the parent of the target, and don't follow a final link */
error = path_lookup(path, LOOKUP_PARENT, nd);
if (error) {
set_errno(-error);
goto out_path_only;
}
parent_dir = nd->dentry->d_inode;
/* make sure the target is there */
dentry = do_lookup(nd->dentry, nd->last.name);
if (!dentry) {
set_errno(ENOENT);
goto out_path_only;
}
/* Make sure the target is not a directory */
if (S_ISDIR(dentry->d_inode->i_mode)) {
set_errno(EISDIR);
goto out_dentry;
}
/* Remove the dentry from its parent */
error = parent_dir->i_op->unlink(parent_dir, dentry);
if (error) {
set_errno(-error);
goto out_dentry;
}
/* Now that our parent doesn't track us, we need to make sure we aren't
* findable via the dentry cache. DYING, so we will be freed in
* dentry_release() */
dentry->d_flags |= DENTRY_DYING;
dcache_remove(dentry->d_sb, dentry);
dentry->d_inode->i_nlink--; /* TODO: race here, esp with a decref */
/* At this point, the dentry is unlinked from the FS, and the inode has one
* less link. When the in-memory objects (dentry, inode) are going to be
* released (after all open files are closed, and maybe after entries are
* evicted from the cache), then nlinks will get checked and the FS-file
* will get removed from the disk */
retval = 0; /* Note the fall through to the exit paths */
out_dentry:
kref_put(&dentry->d_kref);
out_path_only:
path_release(nd);
return retval;
}
/* Checks to see if path can be accessed via mode. Need to actually send the
* mode along somehow, so this doesn't do much now. This is an example of
* decent error propagation from the lower levels via int retvals. */
int do_access(char *path, int mode)
{
struct nameidata nd_r = {0}, *nd = &nd_r;
int retval = 0;
nd->intent = LOOKUP_ACCESS;
retval = path_lookup(path, 0, nd);
path_release(nd);
return retval;
}
int do_file_chmod(struct file *file, int mode)
{
int old_mode_ftype = file->f_dentry->d_inode->i_mode & __S_IFMT;
#if 0
/* TODO: when we have notions of uid, check for the proc's uid */
if (file->f_dentry->d_inode->i_uid != UID_OF_ME)
retval = -EPERM;
else
#endif
file->f_dentry->d_inode->i_mode = (mode & S_PMASK) | old_mode_ftype;
return 0;
}
/* Make a directory at path with mode. Returns -1 and sets errno on errors */
int do_mkdir(char *path, int mode)
{
struct dentry *dentry;
struct inode *parent_i;
struct nameidata nd_r = {0}, *nd = &nd_r;
int error;
int retval = -1;
/* The dir might exist and might be /, so we can't look for the parent */
nd->intent = LOOKUP_OPEN;
error = path_lookup(path, LOOKUP_FOLLOW, nd);
path_release(nd);
if (!error) {
set_errno(EEXIST);
return -1;
}
nd->intent = LOOKUP_CREATE;
/* get the parent, but don't follow links */
error = path_lookup(path, LOOKUP_PARENT, nd);
if (error) {
set_errno(-error);
goto out_path_only;
}
/* Doesn't already exist, let's try to make it: */
dentry = get_dentry(nd->dentry->d_sb, nd->dentry, nd->last.name);
if (!dentry)
goto out_path_only;
parent_i = nd->dentry->d_inode;
if (create_dir(parent_i, dentry, mode))
goto out_dentry;
dcache_put(dentry->d_sb, dentry);
retval = 0; /* Note the fall through to the exit paths */
out_dentry:
kref_put(&dentry->d_kref);
out_path_only:
path_release(nd);
return retval;
}
int do_rmdir(char *path)
{
struct dentry *dentry;
struct inode *parent_i;
struct nameidata nd_r = {0}, *nd = &nd_r;
int error;
int retval = -1;
/* get the parent, following links (probably want this), and we must get a
* directory. Note, current versions of path_lookup can't handle both
* PARENT and DIRECTORY, at least, it doesn't check that *path is a
* directory. */
error = path_lookup(path, LOOKUP_PARENT | LOOKUP_FOLLOW | LOOKUP_DIRECTORY,
nd);
if (error) {
set_errno(-error);
goto out_path_only;
}
/* make sure the target is already there, handle accordingly */
dentry = do_lookup(nd->dentry, nd->last.name);
if (!dentry) {
set_errno(ENOENT);
goto out_path_only;
}
if (!S_ISDIR(dentry->d_inode->i_mode)) {
set_errno(ENOTDIR);
goto out_dentry;
}
if (dentry->d_mount_point) {
set_errno(EBUSY);
goto out_dentry;
}
/* TODO: make sure we aren't a mount or processes root (EBUSY) */
/* Now for the removal. the FSs will check if they are empty */
parent_i = nd->dentry->d_inode;
error = parent_i->i_op->rmdir(parent_i, dentry);
if (error < 0) {
set_errno(-error);
goto out_dentry;
}
/* Now that our parent doesn't track us, we need to make sure we aren't
* findable via the dentry cache. DYING, so we will be freed in
* dentry_release() */
dentry->d_flags |= DENTRY_DYING;
dcache_remove(dentry->d_sb, dentry);
/* Decref ourselves, so inode_release() knows we are done */
dentry->d_inode->i_nlink--;
TAILQ_REMOVE(&nd->dentry->d_subdirs, dentry, d_subdirs_link);
parent_i->i_nlink--; /* TODO: race on this, esp since its a decref */
/* we still have d_parent and a kref on our parent, which will go away when
* the in-memory dentry object goes away. */
retval = 0; /* Note the fall through to the exit paths */
out_dentry:
kref_put(&dentry->d_kref);
out_path_only:
path_release(nd);
return retval;
}
/* Pipes: Doing a simple buffer with reader and writer offsets. Size is power
* of two, so we can easily compute its status and whatnot. */
#define PIPE_SZ (1 << PGSHIFT)
static size_t pipe_get_rd_idx(struct pipe_inode_info *pii)
{
return pii->p_rd_off & (PIPE_SZ - 1);
}
static size_t pipe_get_wr_idx(struct pipe_inode_info *pii)
{
return pii->p_wr_off & (PIPE_SZ - 1);
}
static bool pipe_is_empty(struct pipe_inode_info *pii)
{
return __ring_empty(pii->p_wr_off, pii->p_rd_off);
}
static bool pipe_is_full(struct pipe_inode_info *pii)
{
return __ring_full(PIPE_SZ, pii->p_wr_off, pii->p_rd_off);
}
static size_t pipe_nr_full(struct pipe_inode_info *pii)
{
return __ring_nr_full(pii->p_wr_off, pii->p_rd_off);
}
static size_t pipe_nr_empty(struct pipe_inode_info *pii)
{
return __ring_nr_empty(PIPE_SZ, pii->p_wr_off, pii->p_rd_off);
}
ssize_t pipe_file_read(struct file *file, char *buf, size_t count,
off64_t *offset)
{
struct pipe_inode_info *pii = file->f_dentry->d_inode->i_pipe;
size_t copy_amt, amt_copied = 0;
cv_lock(&pii->p_cv);
while (pipe_is_empty(pii)) {
/* We wait til the pipe is drained before sending EOF if there are no
* writers (instead of aborting immediately) */
if (!pii->p_nr_writers) {
cv_unlock(&pii->p_cv);
return 0;
}
if (file->f_flags & O_NONBLOCK) {
cv_unlock(&pii->p_cv);
set_errno(EAGAIN);
return -1;
}
cv_wait(&pii->p_cv);
cpu_relax();
}
/* We might need to wrap-around with our copy, so we'll do the copy in two
* passes. This will copy up to the end of the buffer, then on the next
* pass will copy the rest to the beginning of the buffer (if necessary) */
for (int i = 0; i < 2; i++) {
copy_amt = MIN(PIPE_SZ - pipe_get_rd_idx(pii),
MIN(pipe_nr_full(pii), count));
assert(current); /* shouldn't pipe from the kernel */
memcpy_to_user(current, buf, pii->p_buf + pipe_get_rd_idx(pii),
copy_amt);
buf += copy_amt;
count -= copy_amt;
pii->p_rd_off += copy_amt;
amt_copied += copy_amt;
}
/* Just using one CV for both readers and writers. We should rarely have
* multiple readers or writers. */
if (amt_copied)
__cv_broadcast(&pii->p_cv);
cv_unlock(&pii->p_cv);
return amt_copied;
}
/* Note: we're not dealing with PIPE_BUF and minimum atomic chunks, unless I
* have to later. */
ssize_t pipe_file_write(struct file *file, const char *buf, size_t count,
off64_t *offset)
{
struct pipe_inode_info *pii = file->f_dentry->d_inode->i_pipe;
size_t copy_amt, amt_copied = 0;
cv_lock(&pii->p_cv);
/* Write aborts right away if there are no readers, regardless of pipe
* status. */
if (!pii->p_nr_readers) {
cv_unlock(&pii->p_cv);
set_errno(EPIPE);
return -1;
}
while (pipe_is_full(pii)) {
if (file->f_flags & O_NONBLOCK) {
cv_unlock(&pii->p_cv);
set_errno(EAGAIN);
return -1;
}
cv_wait(&pii->p_cv);
cpu_relax();
/* Still need to check in the loop, in case the last reader left while
* we slept. */
if (!pii->p_nr_readers) {
cv_unlock(&pii->p_cv);
set_errno(EPIPE);
return -1;
}
}
/* We might need to wrap-around with our copy, so we'll do the copy in two
* passes. This will copy up to the end of the buffer, then on the next
* pass will copy the rest to the beginning of the buffer (if necessary) */
for (int i = 0; i < 2; i++) {
copy_amt = MIN(PIPE_SZ - pipe_get_wr_idx(pii),
MIN(pipe_nr_empty(pii), count));
assert(current); /* shouldn't pipe from the kernel */
memcpy_from_user(current, pii->p_buf + pipe_get_wr_idx(pii), buf,
copy_amt);
buf += copy_amt;
count -= copy_amt;
pii->p_wr_off += copy_amt;
amt_copied += copy_amt;
}
/* Just using one CV for both readers and writers. We should rarely have
* multiple readers or writers. */
if (amt_copied)
__cv_broadcast(&pii->p_cv);
cv_unlock(&pii->p_cv);
return amt_copied;
}
/* In open and release, we need to track the number of readers and writers,
* which we can differentiate by the file flags. */
int pipe_open(struct inode *inode, struct file *file)
{
struct pipe_inode_info *pii = inode->i_pipe;
cv_lock(&pii->p_cv);
/* Ugliness due to not using flags for O_RDONLY and friends... */
if (file->f_mode == S_IRUSR) {
pii->p_nr_readers++;
} else if (file->f_mode == S_IWUSR) {
pii->p_nr_writers++;
} else {
warn("Bad pipe file flags 0x%x\n", file->f_flags);
}
cv_unlock(&pii->p_cv);
return 0;
}
int pipe_release(struct inode *inode, struct file *file)
{
struct pipe_inode_info *pii = inode->i_pipe;
cv_lock(&pii->p_cv);
/* Ugliness due to not using flags for O_RDONLY and friends... */
if (file->f_mode == S_IRUSR) {
pii->p_nr_readers--;
} else if (file->f_mode == S_IWUSR) {
pii->p_nr_writers--;
} else {
warn("Bad pipe file flags 0x%x\n", file->f_flags);
}
/* need to wake up any sleeping readers/writers, since we might be done */
__cv_broadcast(&pii->p_cv);
cv_unlock(&pii->p_cv);
return 0;
}
struct file_operations pipe_f_op = {
.read = pipe_file_read,
.write = pipe_file_write,
.open = pipe_open,
.release = pipe_release,
0
};
void pipe_debug(struct file *f)
{
struct pipe_inode_info *pii = f->f_dentry->d_inode->i_pipe;
assert(pii);
printk("PIPE %p\n", pii);
printk("\trdoff %p\n", pii->p_rd_off);
printk("\twroff %p\n", pii->p_wr_off);
printk("\tnr_rds %d\n", pii->p_nr_readers);
printk("\tnr_wrs %d\n", pii->p_nr_writers);
printk("\tcv waiters %d\n", pii->p_cv.nr_waiters);
}
/* General plan: get a dentry/inode to represent the pipe. We'll alloc it from
* the default_ns SB, but won't actually link it anywhere. It'll only be held
* alive by the krefs, til all the FDs are closed. */
int do_pipe(struct file **pipe_files, int flags)
{
struct dentry *pipe_d;
struct inode *pipe_i;
struct file *pipe_f_read, *pipe_f_write;
struct super_block *def_sb = default_ns.root->mnt_sb;
struct pipe_inode_info *pii;
pipe_d = get_dentry(def_sb, 0, "pipe");
if (!pipe_d)
return -1;
pipe_d->d_op = &dummy_d_op;
pipe_i = get_inode(pipe_d);
if (!pipe_i)
goto error_post_dentry;
/* preemptively mark the dentry for deletion. we have an unlinked dentry
* right off the bat, held in only by the kref chain (pipe_d is the ref). */
pipe_d->d_flags |= DENTRY_DYING;
/* pipe_d->d_inode still has one ref to pipe_i, keeping the inode alive */
kref_put(&pipe_i->i_kref);
/* init inode fields. note we're using the dummy ops for i_op and d_op */
pipe_i->i_mode = S_IRWXU | S_IRWXG | S_IRWXO;
SET_FTYPE(pipe_i->i_mode, __S_IFIFO); /* using type == FIFO */
pipe_i->i_nlink = 1; /* one for the dentry */
pipe_i->i_uid = 0;
pipe_i->i_gid = 0;
pipe_i->i_size = PGSIZE;
pipe_i->i_blocks = 0;
pipe_i->i_atime.tv_sec = 0;
pipe_i->i_atime.tv_nsec = 0;
pipe_i->i_mtime.tv_sec = 0;
pipe_i->i_mtime.tv_nsec = 0;
pipe_i->i_ctime.tv_sec = 0;
pipe_i->i_ctime.tv_nsec = 0;
pipe_i->i_fs_info = 0;
pipe_i->i_op = &dummy_i_op;
pipe_i->i_fop = &pipe_f_op;
pipe_i->i_socket = FALSE;
/* Actually build the pipe. We're using one page, hanging off the
* pipe_inode_info struct. When we release the inode, we free the pipe
* memory too */
pipe_i->i_pipe = kmalloc(sizeof(struct pipe_inode_info), MEM_WAIT);
pii = pipe_i->i_pipe;
if (!pii) {
set_errno(ENOMEM);
goto error_kmalloc;
}
pii->p_buf = kpage_zalloc_addr();
if (!pii->p_buf) {
set_errno(ENOMEM);
goto error_kpage;
}
pii->p_rd_off = 0;
pii->p_wr_off = 0;
pii->p_nr_readers = 0;
pii->p_nr_writers = 0;
cv_init(&pii->p_cv); /* must do this before dentry_open / pipe_open */
/* Now we have an inode for the pipe. We need two files for the read and
* write ends of the pipe. */
flags &= ~(O_ACCMODE); /* avoid user bugs */
pipe_f_read = dentry_open(pipe_d, flags | O_RDONLY);
if (!pipe_f_read)
goto error_f_read;
pipe_f_write = dentry_open(pipe_d, flags | O_WRONLY);
if (!pipe_f_write)
goto error_f_write;
pipe_files[0] = pipe_f_read;
pipe_files[1] = pipe_f_write;
return 0;
error_f_write:
kref_put(&pipe_f_read->f_kref);
error_f_read:
page_decref(kva2page(pii->p_buf));
error_kpage:
kfree(pipe_i->i_pipe);
error_kmalloc:
/* We don't need to free the pipe_i; putting the dentry will free it */
error_post_dentry:
/* Note we only free the dentry on failure. */
kref_put(&pipe_d->d_kref);
return -1;
}
int do_rename(char *old_path, char *new_path)
{
struct nameidata nd_old = {0}, *nd_o = &nd_old;
struct nameidata nd_new = {0}, *nd_n = &nd_new;
struct dentry *old_dir_d, *new_dir_d;
struct inode *old_dir_i, *new_dir_i;
struct dentry *old_d, *new_d, *unlink_d;
int error;
int retval = 0;
struct timespec now;
nd_o->intent = LOOKUP_ACCESS; /* maybe, might need another type */
/* get the parent, but don't follow links */
error = path_lookup(old_path, LOOKUP_PARENT | LOOKUP_DIRECTORY, nd_o);
if (error) {
set_errno(-error);
retval = -1;
goto out_old_path;
}
old_dir_d = nd_o->dentry;
old_dir_i = old_dir_d->d_inode;
old_d = do_lookup(old_dir_d, nd_o->last.name);
if (!old_d) {
set_errno(ENOENT);
retval = -1;
goto out_old_path;
}
nd_n->intent = LOOKUP_CREATE;
error = path_lookup(new_path, LOOKUP_PARENT | LOOKUP_DIRECTORY, nd_n);
if (error) {
set_errno(-error);
retval = -1;
goto out_paths_and_src;
}
new_dir_d = nd_n->dentry;
new_dir_i = new_dir_d->d_inode;
/* TODO if new_dir == old_dir, we might be able to simplify things */
if (new_dir_i->i_sb != old_dir_i->i_sb) {
set_errno(EXDEV);
retval = -1;
goto out_paths_and_src;
}
/* TODO: check_perms is lousy, want to just say "writable" here */
if (check_perms(old_dir_i, S_IWUSR) || check_perms(new_dir_i, S_IWUSR)) {
set_errno(EPERM);
retval = -1;
goto out_paths_and_src;
}
/* TODO: if we're doing a rename that moves a directory, we need to make
* sure the new_path doesn't include the old_path. It's not as simple as
* just checking, since there could be a concurrent rename that breaks the
* check later. e.g. what if new_dir's parent is being moved into a child
* of old_dir?
*
* linux has a per-fs rename mutex for these scenarios, so only one can
* proceed at a time. i don't see another way to deal with it either.
* maybe something like flagging all dentries on the new_path with "do not
* move". */
/* TODO: this is all very racy. right after we do a new_d lookup, someone
* else could create or unlink new_d. need to lock here, or else push this
* into the sub-FS.
*
* For any locking scheme, we probably need to lock both the old and new
* dirs. To prevent deadlock, we need a total ordering of all inodes (or
* dentries, if we locking them instead). inode number or struct inode*
* will work for this. */
new_d = do_lookup(new_dir_d, nd_n->last.name);
if (new_d) {
if (new_d->d_inode == old_d->d_inode)
goto out_paths_and_refs; /* rename does nothing */
/* TODO: Here's a bunch of other racy checks we need to do, maybe in the
* sub-FS:
*
* if src is a dir, dst must be an empty dir if it exists (RACYx2)
* racing on dst being created and it getting new entries
* if src is a file, dst must be a file if it exists (RACY)
* racing on dst being created and still being a file
* racing on dst being unlinked and a new one being added
*/
/* TODO: we should allow empty dirs */
if (S_ISDIR(new_d->d_inode->i_mode)) {
set_errno(EISDIR);
retval = -1;
goto out_paths_and_refs;
}
/* TODO: need this to be atomic with rename */
error = new_dir_i->i_op->unlink(new_dir_i, new_d);
if (error) {
set_errno(-error);
retval = -1;
goto out_paths_and_refs;
}
new_d->d_flags |= DENTRY_DYING;
/* TODO: racy with other lookups on new_d */
dcache_remove(new_d->d_sb, new_d);
new_d->d_inode->i_nlink--; /* TODO: race here, esp with a decref */
kref_put(&new_d->d_kref);
}
/* new_d is just a vessel for the name. somewhat lousy. */
new_d = get_dentry(new_dir_d->d_sb, new_dir_d, nd_n->last.name);
/* TODO: more races. need to remove old_d from the dcache, since we're
* about to change its parentage. could be readded concurrently. */
dcache_remove(old_dir_d->d_sb, old_d);
error = new_dir_i->i_op->rename(old_dir_i, old_d, new_dir_i, new_d);
if (error) {
/* TODO: oh crap, we already unlinked! now we're screwed, and violated
* our atomicity requirements. */
printk("[kernel] rename failed, you might have lost data\n");
set_errno(-error);
retval = -1;
goto out_paths_and_refs;
}
/* old_dir loses old_d, new_dir gains old_d, renamed to new_d. this is
* particularly cumbersome since there are two levels here: the FS has its
* info about where things are, and the VFS has its dentry tree. and it's
* all racy (TODO). */
dentry_set_name(old_d, new_d->d_name.name);
old_d->d_parent = new_d->d_parent;
if (S_ISDIR(old_d->d_inode->i_mode)) {
TAILQ_REMOVE(&old_dir_d->d_subdirs, old_d, d_subdirs_link);
old_dir_i->i_nlink--; /* TODO: racy, etc */
TAILQ_INSERT_TAIL(&new_dir_d->d_subdirs, old_d, d_subdirs_link);
new_dir_i->i_nlink--; /* TODO: racy, etc */
}
/* and then the third level: dcache stuff. we could have old versions of
* old_d or negative versions of new_d sitting around. dcache_put should
* replace a potentially negative dentry for new_d (now called old_d) */
dcache_put(old_dir_d->d_sb, old_d);
/* TODO could have a helper for this, but it's going away soon */
now = nsec2timespec(epoch_nsec());
old_dir_i->i_ctime.tv_sec = now.tv_sec;
old_dir_i->i_mtime.tv_sec = now.tv_sec;
old_dir_i->i_ctime.tv_nsec = now.tv_nsec;
old_dir_i->i_mtime.tv_nsec = now.tv_nsec;
new_dir_i->i_ctime.tv_sec = now.tv_sec;
new_dir_i->i_mtime.tv_sec = now.tv_sec;
new_dir_i->i_ctime.tv_nsec = now.tv_nsec;
new_dir_i->i_mtime.tv_nsec = now.tv_nsec;
/* fall-through */
out_paths_and_refs:
kref_put(&new_d->d_kref);
out_paths_and_src:
kref_put(&old_d->d_kref);
out_paths:
path_release(nd_n);
out_old_path:
path_release(nd_o);
return retval;
}
int do_truncate(struct inode *inode, off64_t len)
{
off64_t old_len;
struct timespec now;
if (len < 0) {
set_errno(EINVAL);
return -1;
}
if (len > PiB) {
printk("[kernel] truncate for > petabyte, probably a bug\n");
/* continuing, not too concerned. could set EINVAL or EFBIG */
}
spin_lock(&inode->i_lock);
old_len = inode->i_size;
if (old_len == len) {
spin_unlock(&inode->i_lock);
return 0;
}
inode->i_size = len;
/* truncate can't block, since we're holding the spinlock. but it can rely
* on that lock being held */
inode->i_op->truncate(inode);
spin_unlock(&inode->i_lock);
if (old_len < len) {
pm_remove_contig(inode->i_mapping, old_len >> PGSHIFT,
(len >> PGSHIFT) - (old_len >> PGSHIFT));
}
now = nsec2timespec(epoch_nsec());
inode->i_ctime.tv_sec = now.tv_sec;
inode->i_mtime.tv_sec = now.tv_sec;
inode->i_ctime.tv_nsec = now.tv_nsec;
inode->i_mtime.tv_nsec = now.tv_nsec;
return 0;
}
struct file *alloc_file(void)
{
struct file *file = kmem_cache_alloc(file_kcache, 0);
if (!file) {
set_errno(ENOMEM);
return 0;
}
/* one for the ref passed out*/
kref_init(&file->f_kref, file_release, 1);
return file;
}
/* Opens and returns the file specified by dentry */
struct file *dentry_open(struct dentry *dentry, int flags)
{
struct inode *inode;
struct file *file;
int desired_mode;
inode = dentry->d_inode;
/* f_mode stores how the OS file is open, which can be more restrictive than
* the i_mode */
desired_mode = omode_to_rwx(flags & O_ACCMODE);
if (check_perms(inode, desired_mode))
goto error_access;
file = alloc_file();
if (!file)
return 0;
file->f_mode = desired_mode;
/* Add to the list of all files of this SB */
TAILQ_INSERT_TAIL(&inode->i_sb->s_files, file, f_list);
kref_get(&dentry->d_kref, 1);
file->f_dentry = dentry;
kref_get(&inode->i_sb->s_mount->mnt_kref, 1);
file->f_vfsmnt = inode->i_sb->s_mount; /* saving a ref to the vmnt...*/
file->f_op = inode->i_fop;
/* Don't store creation flags */
file->f_flags = flags & ~O_CREAT_FLAGS;
file->f_pos = 0;
file->f_uid = inode->i_uid;
file->f_gid = inode->i_gid;
file->f_error = 0;
// struct event_poll_tailq f_ep_links;
spinlock_init(&file->f_ep_lock);
file->f_privdata = 0; /* prob overriden by the fs */
file->f_mapping = inode->i_mapping;
file->f_op->open(inode, file);
return file;
error_access:
set_errno(EACCES);
return 0;
}
/* Closes a file, fsync, whatever else is necessary. Called when the kref hits
* 0. Note that the file is not refcounted on the s_files list, nor is the
* f_mapping refcounted (it is pinned by the i_mapping). */
void file_release(struct kref *kref)
{
struct file *file = container_of(kref, struct file, f_kref);
struct super_block *sb = file->f_dentry->d_sb;
spin_lock(&sb->s_lock);
TAILQ_REMOVE(&sb->s_files, file, f_list);
spin_unlock(&sb->s_lock);
/* TODO: fsync (BLK). also, we may want to parallelize the blocking that
* could happen in here (spawn kernel threads)... */
file->f_op->release(file->f_dentry->d_inode, file);
/* Clean up the other refs we hold */
kref_put(&file->f_dentry->d_kref);
kref_put(&file->f_vfsmnt->mnt_kref);
kmem_cache_free(file_kcache, file);
}
ssize_t kread_file(struct file *file, void *buf, size_t sz)
{
/* TODO: (KFOP) (VFS kernel read/writes need to be from a ktask) */
uintptr_t old_ret = switch_to_ktask();
off64_t dummy = 0;
ssize_t cpy_amt = file->f_op->read(file, buf, sz, &dummy);
switch_back_from_ktask(old_ret);
return cpy_amt;
}
/* Reads the contents of an entire file into a buffer, returning that buffer.
* On error, prints something useful and returns 0 */
void *kread_whole_file(struct file *file)
{
size_t size;
void *contents;
ssize_t cpy_amt;
size = file->f_dentry->d_inode->i_size;
contents = kmalloc(size, MEM_WAIT);
cpy_amt = kread_file(file, contents, size);
if (cpy_amt < 0) {
printk("Error %d reading file %s\n", get_errno(), file_name(file));
kfree(contents);
return 0;
}
if (cpy_amt != size) {
printk("Read %d, needed %d for file %s\n", cpy_amt, size,
file_name(file));
kfree(contents);
return 0;
}
return contents;
}
/* Process-related File management functions */
/* Given any FD, get the appropriate object, 0 o/w. Set vfs if you're looking
* for a file, o/w a chan. Set incref if you want a reference count (which is a
* 9ns thing, you can't use the pointer if you didn't incref). */
void *lookup_fd(struct fd_table *fdt, int fd, bool incref, bool vfs)
{
void *retval = 0;
if (fd < 0)
return 0;
spin_lock(&fdt->lock);
if (fdt->closed) {
spin_unlock(&fdt->lock);
return 0;
}
if (fd < fdt->max_fdset) {
if (GET_BITMASK_BIT(fdt->open_fds->fds_bits, fd)) {
/* while max_files and max_fdset might not line up, we should never
* have a valid fdset higher than files */
assert(fd < fdt->max_files);
if (vfs)
retval = fdt->fd[fd].fd_file;
else
retval = fdt->fd[fd].fd_chan;
/* retval could be 0 if we asked for the wrong one (e.g. it's a
* file, but we asked for a chan) */
if (retval && incref) {
if (vfs)
kref_get(&((struct file*)retval)->f_kref, 1);
else
chan_incref((struct chan*)retval);
}
}
}
spin_unlock(&fdt->lock);
return retval;
}
/* Given any FD, get the appropriate file, 0 o/w */
struct file *get_file_from_fd(struct fd_table *open_files, int file_desc)
{
return lookup_fd(open_files, file_desc, TRUE, TRUE);
}
/* Grow the vfs fd set */
static int grow_fd_set(struct fd_table *open_files)
{
int n;
struct file_desc *nfd, *ofd;
/* Only update open_fds once. If currently pointing to open_fds_init, then
* update it to point to a newly allocated fd_set with space for
* NR_FILE_DESC_MAX */
if (open_files->open_fds == (struct fd_set*)&open_files->open_fds_init) {
open_files->open_fds = kzmalloc(sizeof(struct fd_set), 0);
memmove(open_files->open_fds, &open_files->open_fds_init,
sizeof(struct small_fd_set));
}
/* Grow the open_files->fd array in increments of NR_OPEN_FILES_DEFAULT */
n = open_files->max_files + NR_OPEN_FILES_DEFAULT;
if (n > NR_FILE_DESC_MAX)
return -EMFILE;
nfd = kzmalloc(n * sizeof(struct file_desc), 0);
if (nfd == NULL)
return -ENOMEM;
/* Move the old array on top of the new one */
ofd = open_files->fd;
memmove(nfd, ofd, open_files->max_files * sizeof(struct file_desc));
/* Update the array and the maxes for both max_files and max_fdset */
open_files->fd = nfd;
open_files->max_files = n;
open_files->max_fdset = n;
/* Only free the old one if it wasn't pointing to open_files->fd_array */
if (ofd != open_files->fd_array)
kfree(ofd);
return 0;
}
/* Free the vfs fd set if necessary */
static void free_fd_set(struct fd_table *open_files)
{
void *free_me;
if (open_files->open_fds != (struct fd_set*)&open_files->open_fds_init) {
assert(open_files->fd != open_files->fd_array);
/* need to reset the pointers to the internal addrs, in case we take a
* look while debugging. 0 them out, since they have old data. our
* current versions should all be closed. */
memset(&open_files->open_fds_init, 0, sizeof(struct small_fd_set));
memset(&open_files->fd_array, 0, sizeof(open_files->fd_array));
free_me = open_files->open_fds;
open_files->open_fds = (struct fd_set*)&open_files->open_fds_init;
kfree(free_me);
free_me = open_files->fd;
open_files->fd = open_files->fd_array;
kfree(free_me);
}
}
/* If FD is in the group, remove it, decref it, and return TRUE. */
bool close_fd(struct fd_table *fdt, int fd)
{
struct file *file = 0;
struct chan *chan = 0;
struct fd_tap *tap = 0;
bool ret = FALSE;
if (fd < 0)
return FALSE;
spin_lock(&fdt->lock);
if (fd < fdt->max_fdset) {
if (GET_BITMASK_BIT(fdt->open_fds->fds_bits, fd)) {
/* while max_files and max_fdset might not line up, we should never
* have a valid fdset higher than files */
assert(fd < fdt->max_files);
file = fdt->fd[fd].fd_file;
chan = fdt->fd[fd].fd_chan;
tap = fdt->fd[fd].fd_tap;
fdt->fd[fd].fd_file = 0;
fdt->fd[fd].fd_chan = 0;
fdt->fd[fd].fd_tap = 0;
CLR_BITMASK_BIT(fdt->open_fds->fds_bits, fd);
if (fd < fdt->hint_min_fd)
fdt->hint_min_fd = fd;
ret = TRUE;
}
}
spin_unlock(&fdt->lock);
/* Need to decref/cclose outside of the lock; they could sleep */
if (file)
kref_put(&file->f_kref);
else
cclose(chan);
if (tap)
kref_put(&tap->kref);
return ret;
}
void put_file_from_fd(struct fd_table *open_files, int file_desc)
{
close_fd(open_files, file_desc);
}
static int __get_fd(struct fd_table *open_files, int low_fd, bool must_use_low)
{
int slot = -1;
int error;
bool update_hint = TRUE;
if ((low_fd < 0) || (low_fd > NR_FILE_DESC_MAX))
return -EINVAL;
if (open_files->closed)
return -EINVAL; /* won't matter, they are dying */
if (must_use_low && GET_BITMASK_BIT(open_files->open_fds->fds_bits, low_fd))
return -ENFILE;
if (low_fd > open_files->hint_min_fd)
update_hint = FALSE;
else
low_fd = open_files->hint_min_fd;
/* Loop until we have a valid slot (we grow the fd_array at the bottom of
* the loop if we haven't found a slot in the current array */
while (slot == -1) {
for (low_fd; low_fd < open_files->max_fdset; low_fd++) {
if (GET_BITMASK_BIT(open_files->open_fds->fds_bits, low_fd))
continue;
slot = low_fd;
SET_BITMASK_BIT(open_files->open_fds->fds_bits, slot);
assert(slot < open_files->max_files &&
open_files->fd[slot].fd_file == 0);
/* We know slot >= hint, since we started with the hint */
if (update_hint)
open_files->hint_min_fd = slot + 1;
break;
}
if (slot == -1) {
if ((error = grow_fd_set(open_files)))
return error;
}
}
return slot;
}
/* Insert a file or chan (obj, chosen by vfs) into the fd group with fd_flags.
* If must_use_low, then we have to insert at FD = low_fd. o/w we start looking
* for empty slots at low_fd. */
int insert_obj_fdt(struct fd_table *fdt, void *obj, int low_fd, int fd_flags,
bool must_use_low, bool vfs)
{
int slot;
spin_lock(&fdt->lock);
slot = __get_fd(fdt, low_fd, must_use_low);
if (slot < 0) {
spin_unlock(&fdt->lock);
return slot;
}
assert(slot < fdt->max_files &&
fdt->fd[slot].fd_file == 0);
if (vfs) {
kref_get(&((struct file*)obj)->f_kref, 1);
fdt->fd[slot].fd_file = obj;
fdt->fd[slot].fd_chan = 0;
} else {
chan_incref((struct chan*)obj);
fdt->fd[slot].fd_file = 0;
fdt->fd[slot].fd_chan = obj;
}
fdt->fd[slot].fd_flags = fd_flags;
spin_unlock(&fdt->lock);
return slot;
}
/* Inserts the file in the fd_table, returning the corresponding new file
* descriptor, or an error code. We start looking for open fds from low_fd.
*
* Passing cloexec is a bit cheap, since we might want to expand it to support
* more FD options in the future. */
int insert_file(struct fd_table *open_files, struct file *file, int low_fd,
bool must, bool cloexec)
{
return insert_obj_fdt(open_files, file, low_fd, cloexec ? FD_CLOEXEC : 0,
must, TRUE);
}
/* Closes all open files. Mostly just a "put" for all files. If cloexec, it
* will only close the FDs with FD_CLOEXEC (opened with O_CLOEXEC or fcntld).
*
* Notes on concurrency:
* - Can't hold spinlocks while we call cclose, since it might sleep eventually.
* - We're called from proc_destroy, so we could have concurrent openers trying
* to add to the group (other syscalls), hence the "closed" flag.
* - dot and slash chans are dealt with in proc_free. its difficult to close
* and zero those with concurrent syscalls, since those are a source of krefs.
* - Once we lock and set closed, no further additions can happen. To simplify
* our closes, we also allow multiple calls to this func (though that should
* never happen with the current code). */
void close_fdt(struct fd_table *fdt, bool cloexec)
{
struct file *file;
struct chan *chan;
struct file_desc *to_close;
int idx = 0;
to_close = kzmalloc(sizeof(struct file_desc) * fdt->max_files,
MEM_WAIT);
spin_lock(&fdt->lock);
if (fdt->closed) {
spin_unlock(&fdt->lock);
kfree(to_close);
return;
}
for (int i = 0; i < fdt->max_fdset; i++) {
if (GET_BITMASK_BIT(fdt->open_fds->fds_bits, i)) {
/* while max_files and max_fdset might not line up, we should never
* have a valid fdset higher than files */
assert(i < fdt->max_files);
if (cloexec && !(fdt->fd[i].fd_flags & FD_CLOEXEC))
continue;
file = fdt->fd[i].fd_file;
chan = fdt->fd[i].fd_chan;
to_close[idx].fd_tap = fdt->fd[i].fd_tap;
fdt->fd[i].fd_tap = 0;
if (file) {
fdt->fd[i].fd_file = 0;
to_close[idx++].fd_file = file;
} else {
fdt->fd[i].fd_chan = 0;
to_close[idx++].fd_chan = chan;
}
CLR_BITMASK_BIT(fdt->open_fds->fds_bits, i);
}
}
/* it's just a hint, we can build back up from being 0 */
fdt->hint_min_fd = 0;
if (!cloexec) {
free_fd_set(fdt);
fdt->closed = TRUE;
}
spin_unlock(&fdt->lock);
/* We go through some hoops to close/decref outside the lock. Nice for not
* holding the lock for a while; critical in case the decref/cclose sleeps
* (it can) */
for (int i = 0; i < idx; i++) {
if (to_close[i].fd_file)
kref_put(&to_close[i].fd_file->f_kref);
else
cclose(to_close[i].fd_chan);
if (to_close[i].fd_tap)
kref_put(&to_close[i].fd_tap->kref);
}
kfree(to_close);
}
/* Inserts all of the files from src into dst, used by sys_fork(). */
void clone_fdt(struct fd_table *src, struct fd_table *dst)
{
struct file *file;
struct chan *chan;
int ret;
spin_lock(&src->lock);
if (src->closed) {
spin_unlock(&src->lock);
return;
}
spin_lock(&dst->lock);
if (dst->closed) {
warn("Destination closed before it opened");
spin_unlock(&dst->lock);
spin_unlock(&src->lock);
return;
}
while (src->max_files > dst->max_files) {
ret = grow_fd_set(dst);
if (ret < 0) {
set_error(-ret, "Failed to grow for a clone_fdt");
spin_unlock(&dst->lock);
spin_unlock(&src->lock);
return;
}
}
for (int i = 0; i < src->max_fdset; i++) {
if (GET_BITMASK_BIT(src->open_fds->fds_bits, i)) {
/* while max_files and max_fdset might not line up, we should never
* have a valid fdset higher than files */
assert(i < src->max_files);
file = src->fd[i].fd_file;
chan = src->fd[i].fd_chan;
assert(i < dst->max_files && dst->fd[i].fd_file == 0);
SET_BITMASK_BIT(dst->open_fds->fds_bits, i);
dst->fd[i].fd_file = file;
dst->fd[i].fd_chan = chan;
if (file)
kref_get(&file->f_kref, 1);
else
chan_incref(chan);
}
}
dst->hint_min_fd = src->hint_min_fd;
spin_unlock(&dst->lock);
spin_unlock(&src->lock);
}
static void __chpwd(struct fs_struct *fs_env, struct dentry *new_pwd)
{
struct dentry *old_pwd;
kref_get(&new_pwd->d_kref, 1);
/* writer lock, make sure we replace pwd with ours. could also CAS.
* readers don't lock at all, so they need to either loop, or we need to
* delay releasing old_pwd til an RCU grace period. */
spin_lock(&fs_env->lock);
old_pwd = fs_env->pwd;
fs_env->pwd = new_pwd;
spin_unlock(&fs_env->lock);
kref_put(&old_pwd->d_kref);
}
/* Change the working directory of the given fs env (one per process, at this
* point). Returns 0 for success, sets errno and returns -1 otherwise. */
int do_chdir(struct fs_struct *fs_env, char *path)
{
struct nameidata nd_r = {0}, *nd = &nd_r;
int error;
error = path_lookup(path, LOOKUP_DIRECTORY, nd);
if (error) {
set_errno(-error);
path_release(nd);
return -1;
}
/* nd->dentry is the place we want our PWD to be */
__chpwd(fs_env, nd->dentry);
path_release(nd);
return 0;
}
int do_fchdir(struct fs_struct *fs_env, struct file *file)
{
if ((file->f_dentry->d_inode->i_mode & __S_IFMT) != __S_IFDIR) {
set_errno(ENOTDIR);
return -1;
}
__chpwd(fs_env, file->f_dentry);
return 0;
}
/* Returns a null-terminated string of up to length cwd_l containing the
* absolute path of fs_env, (up to fs_env's root). Be sure to kfree the char*
* "kfree_this" when you are done with it. We do this since it's easier to
* build this string going backwards. Note cwd_l is not a strlen, it's an
* absolute size. */
char *do_getcwd(struct fs_struct *fs_env, char **kfree_this, size_t cwd_l)
{
struct dentry *dentry = fs_env->pwd;
size_t link_len;
char *path_start, *kbuf;
if (cwd_l < 2) {
set_errno(ERANGE);
return 0;
}
kbuf = kmalloc(cwd_l, 0);
if (!kbuf) {
set_errno(ENOMEM);
return 0;
}
*kfree_this = kbuf;
kbuf[cwd_l - 1] = '\0';
kbuf[cwd_l - 2] = '/';
/* for each dentry in the path, all the way back to the root of fs_env, we
* grab the dentry name, push path_start back enough, and write in the name,
* using /'s to terminate. We skip the root, since we don't want its
* actual name, just "/", which is set before each loop. */
path_start = kbuf + cwd_l - 2; /* the last byte written */
while (dentry != fs_env->root) {
link_len = dentry->d_name.len; /* this does not count the \0 */
if (path_start - (link_len + 2) < kbuf) {
kfree(kbuf);
set_errno(ERANGE);
return 0;
}
path_start -= link_len;
memmove(path_start, dentry->d_name.name, link_len);
path_start--;
*path_start = '/';
dentry = dentry->d_parent;
}
return path_start;
}
static void print_dir(struct dentry *dentry, char *buf, int depth)
{
struct dentry *child_d;
struct dirent next = {0};
struct file *dir;
int retval;
if (!S_ISDIR(dentry->d_inode->i_mode)) {
warn("Thought this was only directories!!");
return;
}
/* Print this dentry */
printk("%s%s/ nlink: %d\n", buf, dentry->d_name.name,
dentry->d_inode->i_nlink);
if (dentry->d_mount_point) {
dentry = dentry->d_mounted_fs->mnt_root;
}
if (depth >= 32)
return;
/* Set buffer for our kids */
buf[depth] = '\t';
dir = dentry_open(dentry, 0);
if (!dir)
panic("Filesystem seems inconsistent - unable to open a dir!");
/* Process every child, recursing on directories */
while (1) {
retval = dir->f_op->readdir(dir, &next);
if (retval >= 0) {
/* Skip .., ., and empty entries */
if (!strcmp("..", next.d_name) || !strcmp(".", next.d_name) ||
next.d_ino == 0)
goto loop_next;
/* there is an entry, now get its dentry */
child_d = do_lookup(dentry, next.d_name);
if (!child_d)
panic("Inconsistent FS, dirent doesn't have a dentry!");
/* Recurse for directories, or just print the name for others */
switch (child_d->d_inode->i_mode & __S_IFMT) {
case (__S_IFDIR):
print_dir(child_d, buf, depth + 1);
break;
case (__S_IFREG):
printk("%s%s size(B): %d nlink: %d\n", buf, next.d_name,
child_d->d_inode->i_size, child_d->d_inode->i_nlink);
break;
case (__S_IFLNK):
printk("%s%s -> %s\n", buf, next.d_name,
child_d->d_inode->i_op->readlink(child_d));
break;
case (__S_IFCHR):
printk("%s%s (char device) nlink: %d\n", buf, next.d_name,
child_d->d_inode->i_nlink);
break;
case (__S_IFBLK):
printk("%s%s (block device) nlink: %d\n", buf, next.d_name,
child_d->d_inode->i_nlink);
break;
default:
warn("Look around you! Unknown filetype!");
}
kref_put(&child_d->d_kref);
}
loop_next:
if (retval <= 0)
break;
}
/* Reset buffer to the way it was */
buf[depth] = '\0';
kref_put(&dir->f_kref);
}
/* Debugging */
int ls_dash_r(char *path)
{
struct nameidata nd_r = {0}, *nd = &nd_r;
int error;
char buf[32] = {0};
error = path_lookup(path, LOOKUP_ACCESS | LOOKUP_DIRECTORY, nd);
if (error) {
path_release(nd);
return error;
}
print_dir(nd->dentry, buf, 0);
path_release(nd);
return 0;
}
/* Dummy ops, to catch weird operations we weren't expecting */
int dummy_create(struct inode *dir, struct dentry *dentry, int mode,
struct nameidata *nd)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
struct dentry *dummy_lookup(struct inode *dir, struct dentry *dentry,
struct nameidata *nd)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return 0;
}
int dummy_link(struct dentry *old_dentry, struct inode *dir,
struct dentry *new_dentry)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_unlink(struct inode *dir, struct dentry *dentry)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_rmdir(struct inode *dir, struct dentry *dentry)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t rdev)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
char *dummy_readlink(struct dentry *dentry)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return 0;
}
void dummy_truncate(struct inode *inode)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
}
int dummy_permission(struct inode *inode, int mode, struct nameidata *nd)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_d_revalidate(struct dentry *dir, struct nameidata *nd)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_d_hash(struct dentry *dentry, struct qstr *name)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_d_compare(struct dentry *dir, struct qstr *name1, struct qstr *name2)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_d_delete(struct dentry *dentry)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
int dummy_d_release(struct dentry *dentry)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
return -1;
}
void dummy_d_iput(struct dentry *dentry, struct inode *inode)
{
printk("Dummy VFS function %s called!\n", __FUNCTION__);
}
struct inode_operations dummy_i_op = {
dummy_create,
dummy_lookup,
dummy_link,
dummy_unlink,
dummy_symlink,
dummy_mkdir,
dummy_rmdir,
dummy_mknod,
dummy_rename,
dummy_readlink,
dummy_truncate,
dummy_permission,
};
struct dentry_operations dummy_d_op = {
dummy_d_revalidate,
dummy_d_hash,
dummy_d_compare,
dummy_d_delete,
dummy_d_release,
dummy_d_iput,
};