/* Copyright (c) 2010 The Regents of the University of California
 * Barret Rhoden <brho@cs.berkeley.edu>
 * See LICENSE for details.
 *
 * Ext2, VFS required functions, internal functions, life, the universe, and
 * everything! */

#include <vfs.h>
#include <ext2fs.h>
#include <blockdev.h>
#include <kmalloc.h>
#include <assert.h>
#include <kref.h>
#include <endian.h>
#include <error.h>
#include <pmap.h>
#include <bitmask.h>

/* These structs are declared again and initialized farther down */
struct page_map_operations ext2_pm_op;
struct super_operations ext2_s_op;
struct inode_operations ext2_i_op;
struct dentry_operations ext2_d_op;
struct file_operations ext2_f_op_file;
struct file_operations ext2_f_op_dir;
struct file_operations ext2_f_op_sym;

/* EXT2 Internal Functions */

/* Useful helper functions. */

/* Returns the block group ID of the BG containing the inode.  BGs start with 0,
 * inodes are indexed starting at 1. */
static struct ext2_block_group *ext2_inode2bg(struct inode *inode)
{
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)inode->i_sb->s_fs_info;
	unsigned int bg_num = (inode->i_ino - 1) /
	                      le32_to_cpu(e2sbi->e2sb->s_inodes_per_group);
	return &e2sbi->e2bg[bg_num];
}

/* This returns the inode's 0-index within a block group */
static unsigned int ext2_inode2bgidx(struct inode *inode)
{
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)inode->i_sb->s_fs_info;
	return (inode->i_ino - 1) % le32_to_cpu(e2sbi->e2sb->s_inodes_per_group);
}

/* Returns the inode number given a 0-index of an inode within a block group */
static unsigned long ext2_bgidx2ino(struct super_block *sb,
                                    struct ext2_block_group *bg,
                                    unsigned int ino_idx)
{
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)sb->s_fs_info;
	struct ext2_sb *e2sb = e2sbi->e2sb;
	struct ext2_block_group *e2bg = e2sbi->e2bg;
	return (bg - e2bg) * le32_to_cpu(e2sb->s_inodes_per_group) + ino_idx + 1;
}

/* Returns an uncounted reference to the BG in the BG table, which is pinned,
 * hanging off the sb.  Note, the BGs cover the blocks starting from the first
 * data block, not from 0.  So if the FDB is 1, BG 0 covers 1 through 1024, and
 * not 0 through 1023. */
static struct ext2_block_group *ext2_block2bg(struct super_block *sb,
                                              uint32_t blk_num)
{
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)sb->s_fs_info;
	unsigned int bg_num;
	bg_num = (blk_num - le32_to_cpu(e2sbi->e2sb->s_first_data_block)) /
	         le32_to_cpu(e2sbi->e2sb->s_blocks_per_group);
	return &e2sbi->e2bg[bg_num];
}

/* This returns the block's 0-index within a block group.  Note all blocks are
 * offset by FDB when dealing with BG membership. */
static unsigned int ext2_block2bgidx(struct super_block *sb, uint32_t blk_num)
{
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)sb->s_fs_info;
	return (blk_num - le32_to_cpu(e2sbi->e2sb->s_first_data_block)) %
	       le32_to_cpu(e2sbi->e2sb->s_blocks_per_group);
}

/* Returns the FS block for the given BG's idx block */
static uint32_t ext2_bgidx2block(struct super_block *sb,
                                 struct ext2_block_group *bg,
                                 unsigned int blk_idx)
{
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)sb->s_fs_info;
	struct ext2_sb *e2sb = e2sbi->e2sb;
	struct ext2_block_group *e2bg = e2sbi->e2bg;
	return (bg - e2bg) * le32_to_cpu(e2sb->s_blocks_per_group) + blk_idx +
	       le32_to_cpu(e2sb->s_first_data_block);
}

/* Slabs for ext2 specific info chunks */
struct kmem_cache *ext2_i_kcache;

/* One-time init for all ext2 instances */
void ext2_init(void)
{
	ext2_i_kcache = kmem_cache_create("ext2_i_info", sizeof(struct ext2_i_info),
	                                  __alignof__(struct ext2_i_info), 0, 0, 0);
}

/* Block management */

/* TODO: pull these metablock functions out of ext2 */
/* Makes sure the FS block of metadata is in memory.  This returns a pointer to
 * the beginning of the requested block.  Release it with put_metablock().
 * Internally, the kreffing is done on the page. */
void *__ext2_get_metablock(struct block_device *bdev, unsigned long blk_num,
                           unsigned int blk_sz)
{
	return bdev_get_buffer(bdev, blk_num, blk_sz)->bh_buffer;
}

/* Convenience wrapper */
void *ext2_get_metablock(struct super_block *sb, unsigned long block_num)
{
	return __ext2_get_metablock(sb->s_bdev, block_num, sb->s_blocksize);
}

/* Helper to figure out the BH for any address within it's buffer */
static struct buffer_head *ext2_my_bh(struct super_block *sb, void *addr)
{
	struct page *page = kva2page(addr);
	struct buffer_head *bh = (struct buffer_head*)page->pg_private;
	/* This case is for when we try do decref a non-BH'd 'metablock'.  It's tied
	 * to e2ii->i_block[]. */
	if (!bh)
		return 0;
	void *my_buf = (void*)ROUNDDOWN((uintptr_t)addr, sb->s_blocksize);
	while (bh) {
		if (bh->bh_buffer == my_buf)
			break;
		bh = bh->bh_next;
	}
	assert(bh && bh->bh_buffer == my_buf);
	return bh;
}

/* Decrefs the buffer from get_metablock().  Call this when you no longer
 * reference your metadata block/buffer.  Yes, we could just decref the page,
 * but this will work if we end up changing how bdev_put_buffer() works. */
void ext2_put_metablock(struct super_block *sb, void *buffer)
{
	struct buffer_head *bh = ext2_my_bh(sb, buffer);
	if (bh)
		bdev_put_buffer(bh);
}

/* Will dirty the block/BH/page for the given metadata block/buffer. */
void ext2_dirty_metablock(struct super_block *sb, void *buffer)
{
	struct buffer_head *bh = ext2_my_bh(sb, buffer);
	if (bh)
		bdev_dirty_buffer(bh);
}

/* Helper for alloc_block.  It will try to alloc a block from the BG, starting
 * with blk_idx (relative number within the BG).   If successful, it will return
 * the FS block number via *block_num.  TODO: concurrency protection */
static bool ext2_tryalloc(struct super_block *sb, struct ext2_block_group *bg,
                          unsigned int blk_idx, uint32_t *block_num)
{
	uint8_t *blk_bitmap;
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)sb->s_fs_info;
	unsigned int blks_per_bg = le32_to_cpu(e2sbi->e2sb->s_blocks_per_group);
	bool found = FALSE;

	/* Check to see if there are any free blocks */
	if (!le32_to_cpu(bg->bg_free_blocks_cnt))
		return FALSE;
	/* Check the bitmap for your desired block.  We'll loop through the whole
	 * BG, starting with the one we want first. */
	blk_bitmap = ext2_get_metablock(sb, bg->bg_block_bitmap);
	for (int i = 0; i < blks_per_bg; i++) {
		if (!(GET_BITMASK_BIT(blk_bitmap, blk_idx))) {
			SET_BITMASK_BIT(blk_bitmap, blk_idx);
			bg->bg_free_blocks_cnt--;
			ext2_dirty_metablock(sb, blk_bitmap);
			found = TRUE;
			break;
		}
		/* Note: the wrap-around hasn't been tested yet */
		blk_idx = (blk_idx + 1) % blks_per_bg;
	}
	ext2_put_metablock(sb, blk_bitmap);
	if (found)
		*block_num = ext2_bgidx2block(sb, bg, blk_idx);
	return found;
}

/* This allocates a fresh block for the inode, preferably 'fetish' (name
 * courtesy of L.F.), returning the FS block number that's been allocated.
 * Note, Linux does some block preallocation here.  Consider doing the same (off
 * the in-memory inode).  Note the lack of concurrency protections here. */
uint32_t ext2_alloc_block(struct inode *inode, uint32_t fetish)
{
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)inode->i_sb->s_fs_info;
	struct ext2_block_group *fetish_bg, *bg_i = e2sbi->e2bg;
	unsigned int blk_idx;
	bool found = FALSE;
	uint32_t retval = 0;

	/* Get our ideal starting point */
	fetish_bg = ext2_block2bg(inode->i_sb, fetish);
	blk_idx = ext2_block2bgidx(inode->i_sb, fetish);
	/* Try to find a free block in the BG of the one we desire */
	found = ext2_tryalloc(inode->i_sb, fetish_bg, blk_idx, &retval);
	if (found)
		return retval;

	warn("This part hasn't been tested yet.");
	/* Find a block anywhere else (perhaps using the log trick, but for now just
	 * linearly scanning). */
	for (int i = 0; i < e2sbi->nr_bgs; i++, bg_i++) {
		if (bg_i == fetish_bg)
			continue;
		found = ext2_tryalloc(inode->i_sb, bg_i, 0, &retval);
		if (found)
			break;
	}
	if (!found)
		panic("Ran out of blocks! (probably a bug)");
	return retval;
}

/* Inode Management */

/* Helper for alloc_diskinode.  It will try to alloc a disk inode from the BG.
 * If successful, it will return the inode number in *ino_num.  TODO:
 * concurrency protection */
static bool ext2_tryalloc_diskinode(struct super_block *sb,
                                    struct ext2_block_group *bg,
                                    unsigned long *ino_num)
{
	uint8_t *ino_bitmap;
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)sb->s_fs_info;
	unsigned int i, ino_per_bg = le32_to_cpu(e2sbi->e2sb->s_inodes_per_group);
	bool found = FALSE;

	/* Check to see if there are any free inodes */
	if (!le32_to_cpu(bg->bg_free_inodes_cnt))
		return FALSE;
	/* Check the bitmap for the free inode */
	ino_bitmap = ext2_get_metablock(sb, bg->bg_inode_bitmap);
	for (i = 0; i < ino_per_bg; i++) {
		if (!(GET_BITMASK_BIT(ino_bitmap, i))) {
			SET_BITMASK_BIT(ino_bitmap, i);
			bg->bg_free_inodes_cnt--;
			ext2_dirty_metablock(sb, ino_bitmap);
			found = TRUE;
			break;
		}
	}
	ext2_put_metablock(sb, ino_bitmap);
	/* Convert the i (a 0-index bit)  within the BG to a real inode number. */
	if (found)
		*ino_num = ext2_bgidx2ino(sb, bg, i);
	return found;
}

/* This allocates a fresh ino number for inode, given the parent's BG.  Make
 * sure you set the inode's type before calling this, since it matters if we a
 * making a directory or not.  This disk inode is reserved on disk in the bitmap
 * (at least the bitmap is changed and dirtied).  Note the lack of concurrency
 * protections here.  Consider returning the BG too. */
unsigned long ext2_alloc_diskinode(struct inode *inode,
                                   struct ext2_block_group *dir_bg)
{
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)inode->i_sb->s_fs_info;
	struct ext2_block_group *bg = dir_bg;
	struct ext2_block_group *bg_i = e2sbi->e2bg;
	bool found = FALSE;
	unsigned long retval = 0;

	if (S_ISDIR(inode->i_mode)) {
		/* TODO: intelligently pick a different bg to use than the current one.
		 * Right now, we just jump to the next one, though you should do things
		 * like take into account the ratio of directories to files. */
		bg += 1;
	}
	/* Try to find a free inode in the chosen BG */
	found = ext2_tryalloc_diskinode(inode->i_sb, bg, &retval);
	if (found)
		return retval;

	warn("This part hasn't been tested yet.");
	/* Find an inode anywhere else (perhaps using the log trick, but for now just
	 * linearly scanning). */
	for (int i = 0; i < e2sbi->nr_bgs; i++, bg_i++) {
		if (bg_i == bg)
			continue;
		found = ext2_tryalloc_diskinode(inode->i_sb, bg_i, &retval);
		if (found)
			break;
	}
	if (!found)
		panic("Ran out of inodes! (probably a bug)");
	return retval;
}

/* Helper for ino table management.  blkid is the inode table block we are
 * looking in, rel_blkid is the block we want, relative to the current
 * threshhold for a level of indirection, and reach is how many items a given
 * slot indexes.  Returns a pointer to the slot for the given block. */
static uint32_t *ext2_find_inotable_slot(struct inode *inode, uint32_t blkid,
                                         uint32_t rel_blkid,
                                         unsigned int reach)
{
	uint32_t *blk_buf = ext2_get_metablock(inode->i_sb, blkid);
	assert(blk_buf);
	return &blk_buf[rel_blkid / reach];
}

/* If blk_slot is empty (no block mapped there) it will alloc and link a new
 * block.  This is only used for allocating a block to be an indirect table
 * (it's grabbing a metablock, we have no hint, and it handles the buffer
 * differently than for a file page/buffer). */
static void ext2_fill_inotable_slot(struct inode *inode, uint32_t *blk_slot)
{
	uint32_t new_blkid, hint_blk;
	void *new_blk;

	if (le32_to_cpu(*blk_slot))
		return;
	/* Use any block in our inode's BG as a hint for the indirect block */
	hint_blk = ext2_bgidx2block(inode->i_sb, ext2_inode2bg(inode), 0);
	new_blkid = ext2_alloc_block(inode, hint_blk);
	/* Actually read in the block we alloc'd */
	new_blk = ext2_get_metablock(inode->i_sb, new_blkid);
	memset(new_blk, 0, inode->i_sb->s_blocksize);
	ext2_dirty_metablock(inode->i_sb, new_blk);
	/* We put it, despite it getting relooked up in the next walk */
	ext2_put_metablock(inode->i_sb, new_blk);
	/* Now write the new block into its slot */
	*blk_slot = cpu_to_le32(new_blkid);
	ext2_dirty_metablock(inode->i_sb, blk_slot);
}

/* This walks a table stored at block 'blkid', returning which block you should
 * walk next in 'blkid'.  rel_inoblk is where you are given the current level of
 * indirection tables, and returns where you should be for the next one.  Reach
 * is how many items the current table's *items* can index (so if we're on a
 * 3x indir block, reach should be for the doubly-indirect entries, and
 * rel_inoblk will tell you where within that double block you want).
 *
 * This will also alloc intermediate tables if there isn't one already (TODO:
 * concurrency protection on modifying the table). */
static void ext2_walk_inotable(struct inode *inode, uint32_t *blkid,
                               uint32_t *rel_inoblk, unsigned int reach)
{
	uint32_t *blk_slot;
	blk_slot = ext2_find_inotable_slot(inode, *blkid, *rel_inoblk, reach);
	/* We could only do this based on a bool, but if we're trying to walk it,
	 * we ought to want to alloc if there is no block. */
	ext2_fill_inotable_slot(inode, blk_slot);
	*blkid = le32_to_cpu(*blk_slot);
	*rel_inoblk = *rel_inoblk % reach;
	ext2_put_metablock(inode->i_sb, blk_slot);	/* ref for the one looked in */
}

/* Finds the slot of the FS block corresponding to a specific block number of an
 * inode.  It does this by walking the inode's tables.  The general idea is that
 * if the ino_block num is above a threshold, we'll need to go into indirect
 * tables (1x, 2x, or 3x (triply indirect) tables).  Block numbers start at 0.
 *
 * This returns a pointer within a metablock, which needs to be decref'd (and
 * possibly dirtied) when you are done.  Note, it can return a pointer to
 * something that is NOT in a metablock (e2ii->i_block[]), but put_metablock can
 * handle it for now.
 *
 * Horrendously untested, btw. */
uint32_t *ext2_lookup_inotable_slot(struct inode *inode, uint32_t ino_block)
{
	struct ext2_i_info *e2ii = (struct ext2_i_info*)inode->i_fs_info;

	uint32_t blkid, *blk_slot;
	/* The 'reach' is how many blocks a given table can 'address' */
	int ptrs_per_blk = inode->i_sb->s_blocksize / sizeof(uint32_t);
	int reach_1xblk = ptrs_per_blk;
	int reach_2xblk = ptrs_per_blk * ptrs_per_blk;
	/* thresholds are the first blocks that require a level of indirection */
	int single_threshold = 12;
	int double_threshold = single_threshold + reach_1xblk;
	int triple_threshold = double_threshold + reach_2xblk;
	/* this is the desired block num lookup within a level of indirection.  It
	 * will need to be offset based on what level of lookups we want (try it in
	 * your head with 12 first). */
	uint32_t rel_inoblk;

	if (ino_block >= triple_threshold) {
		/* ino_block requires a triply-indirect lookup */
		rel_inoblk = ino_block - triple_threshold;
		/* Make sure a 14 block (3x indirect) is there */
		ext2_fill_inotable_slot(inode, &e2ii->i_block[14]);
		blkid = e2ii->i_block[14];
		ext2_walk_inotable(inode, &blkid, &rel_inoblk, reach_2xblk);
		ext2_walk_inotable(inode, &blkid, &rel_inoblk, reach_1xblk);
		blk_slot = ext2_find_inotable_slot(inode, blkid, rel_inoblk, 1);
	} else if (ino_block >= double_threshold) {
		/* ino_block requires a doubly-indirect lookup  */
		rel_inoblk = ino_block - double_threshold;
		ext2_fill_inotable_slot(inode, &e2ii->i_block[13]);
		blkid = e2ii->i_block[13];
		ext2_walk_inotable(inode, &blkid, &rel_inoblk, reach_1xblk);
		blk_slot = ext2_find_inotable_slot(inode, blkid, rel_inoblk, 1);
	} else if (ino_block >= single_threshold) {
		/* ino_block requires a singly-indirect lookup */
		rel_inoblk = ino_block - single_threshold;
		ext2_fill_inotable_slot(inode, &e2ii->i_block[12]);
		blkid = e2ii->i_block[12];
		blk_slot = ext2_find_inotable_slot(inode, blkid, rel_inoblk, 1);
	} else {
		/* Direct block, straight out of the inode */
		blk_slot = &e2ii->i_block[ino_block];
	}
	return blk_slot;
}

/* Determines the FS block id for a given inode block id.  Convenience wrapper
 * that may go away soon. */
uint32_t ext2_find_inoblock(struct inode *inode, unsigned int ino_block)
{
	uint32_t retval, *buf = ext2_lookup_inotable_slot(inode, ino_block);
	retval = *buf;
	ext2_put_metablock(inode->i_sb, buf);
	return retval;
}

/* Returns an incref'd metadata block for the contents of the ino block.  Don't
 * use this for regular files - use their inode's page cache instead (used for
 * directories for now).  If there isn't a block allocated yet, it will provide
 * a zeroed one. */
void *ext2_get_ino_metablock(struct inode *inode, unsigned long ino_block)
{
	uint32_t blkid, *retval, *blk_slot;
	blk_slot = ext2_lookup_inotable_slot(inode, ino_block);
	blkid = le32_to_cpu(*blk_slot);
	if (blkid) {
		ext2_put_metablock(inode->i_sb, blk_slot);
		return ext2_get_metablock(inode->i_sb, blkid);
	}
	/* If there isn't a block there, alloc and insert one.  This block will be
	 * the next big chunk of "file" data for this inode. */
	blkid = ext2_alloc_block(inode, ext2_bgidx2block(inode->i_sb,
	                                                 ext2_inode2bg(inode),
	                                                 0));
	*blk_slot = cpu_to_le32(blkid);
	ext2_dirty_metablock(inode->i_sb, blk_slot);
	ext2_put_metablock(inode->i_sb, blk_slot);
	inode->i_blocks += inode->i_sb->s_blocksize >> 9;	/* inc by 1 FS block */
	inode->i_size += inode->i_sb->s_blocksize;
	retval = ext2_get_metablock(inode->i_sb, blkid);
	memset(retval, 0, inode->i_sb->s_blocksize);		/* 0 the new block */
	return retval;
}

/* This should help with degubbing.  In read_inode(), print out the i_block, and
 * consider manually (via memory inspection) examining those blocks.  Odds are,
 * the 2x and 3x walks are jacked up. */
void ext2_print_ino_blocks(struct inode *inode)
{
	printk("Inode %p, Size: %d, 512B 'blocks': %d\n-------------\n", inode,
	       inode->i_size, inode->i_blocks);
	for (int i = 0; i < inode->i_blocks * (inode->i_sb->s_blocksize / 512); i++)
		printk("# %03d, Block %03d\n", i, ext2_find_inoblock(inode, i));
}

/* Misc Functions */

/* This checks an ext2 disc SB for consistency, optionally printing out its
 * stats.  It also will also read in a copy of the block group descriptor table
 * from its first location (right after the primary SB copy) */
void ext2_check_sb(struct ext2_sb *e2sb, struct ext2_block_group *bg,
                   bool print)
{
	int retval;
	unsigned int blksize, blks_per_group, num_blk_group, num_blks;
	unsigned int inodes_per_grp, inode_size;
	unsigned int sum_blks = 0, sum_inodes = 0;

	assert(le16_to_cpu(e2sb->s_magic) == EXT2_SUPER_MAGIC);
	num_blks = le32_to_cpu(e2sb->s_blocks_cnt);
	blksize = 1024 << le32_to_cpu(e2sb->s_log_block_size);
	blks_per_group = le32_to_cpu(e2sb->s_blocks_per_group);
	num_blk_group = num_blks / blks_per_group + (num_blks % blks_per_group ? 1 : 0);

	if (print) {
		printk("EXT2 info:\n-------------------------\n");
		printk("Total Inodes:     %8d\n", le32_to_cpu(e2sb->s_inodes_cnt));
		printk("Total Blocks:     %8d\n", le32_to_cpu(e2sb->s_blocks_cnt));
		printk("Num R-Blocks:     %8d\n", le32_to_cpu(e2sb->s_rblocks_cnt));
		printk("Num Free Blocks:  %8d\n", le32_to_cpu(e2sb->s_free_blocks_cnt));
		printk("Num Free Inodes:  %8d\n", le32_to_cpu(e2sb->s_free_inodes_cnt));
		printk("First Data Block: %8d\n",
		       le32_to_cpu(e2sb->s_first_data_block));
		printk("Block Size:       %8d\n",
		       1024 << le32_to_cpu(e2sb->s_log_block_size));
		printk("Fragment Size:    %8d\n",
		       1024 << le32_to_cpu(e2sb->s_log_frag_size));
		printk("Blocks per group: %8d\n",
		       le32_to_cpu(e2sb->s_blocks_per_group));
		printk("Inodes per group: %8d\n",
		       le32_to_cpu(e2sb->s_inodes_per_group));
		printk("Block groups:     %8d\n", num_blk_group);
		printk("Mount state:      %8d\n", le16_to_cpu(e2sb->s_state));
		printk("Rev Level:        %8d\n", le32_to_cpu(e2sb->s_minor_rev_level));
		printk("Minor Rev Level:  %8d\n", le16_to_cpu(e2sb->s_minor_rev_level));
		printk("Creator OS:       %8d\n", le32_to_cpu(e2sb->s_creator_os));
		printk("First Inode:      %8d\n", le32_to_cpu(e2sb->s_first_ino));
		printk("Inode size:       %8d\n", le16_to_cpu(e2sb->s_inode_size));
		printk("This block group: %8d\n", le16_to_cpu(e2sb->s_block_group_nr));
		printk("BG ID of 1st meta:%8d\n", le16_to_cpu(e2sb->s_first_meta_bg));
		printk("Volume name:      %s\n", e2sb->s_volume_name);
		printk("\nBlock Group Info:\n----------------------\n");
	}

	for (int i = 0; i < num_blk_group; i++) {
		sum_blks += le16_to_cpu(bg[i].bg_free_blocks_cnt);
		sum_inodes += le16_to_cpu(bg[i].bg_free_inodes_cnt);
		if (print) {
			printk("*** BG %d at %p\n", i, &bg[i]);
			printk("Block bitmap:%8d\n", le32_to_cpu(bg[i].bg_block_bitmap));
			printk("Inode bitmap:%8d\n", le32_to_cpu(bg[i].bg_inode_bitmap));
			printk("Inode table: %8d\n", le32_to_cpu(bg[i].bg_inode_table));
			printk("Free blocks: %8d\n", le16_to_cpu(bg[i].bg_free_blocks_cnt));
			printk("Free inodes: %8d\n", le16_to_cpu(bg[i].bg_free_inodes_cnt));
			printk("Used Dirs:   %8d\n", le16_to_cpu(bg[i].bg_used_dirs_cnt));
		}
	}

	/* Sanity Assertions.  A good ext2 will always pass these. */
	inodes_per_grp = le32_to_cpu(e2sb->s_inodes_per_group);
	blks_per_group = le32_to_cpu(e2sb->s_blocks_per_group);
	inode_size = le32_to_cpu(e2sb->s_inode_size);
	assert(le32_to_cpu(e2sb->s_inodes_cnt) <= inodes_per_grp * num_blk_group);
	assert(le32_to_cpu(e2sb->s_free_inodes_cnt) == sum_inodes);
	assert(le32_to_cpu(e2sb->s_blocks_cnt) <= blks_per_group * num_blk_group);
	assert(le32_to_cpu(e2sb->s_free_blocks_cnt) == sum_blks);
	if (blksize == 1024)
		assert(le32_to_cpu(e2sb->s_first_data_block) == 1);
	else
		assert(le32_to_cpu(e2sb->s_first_data_block) == 0);
	assert(inode_size <= blksize);
	assert(inode_size == 1 << LOG2_UP(inode_size));
	assert(blksize * 8 >= inodes_per_grp);
	assert(inodes_per_grp % (blksize / inode_size) == 0);
	if (print)
		printk("Passed EXT2 Checks\n");
}

/* VFS required Misc Functions */

/* Creates the SB.  Like with Ext2's, we should consider pulling out the
 * FS-independent stuff, if possible. */
struct super_block *ext2_get_sb(struct fs_type *fs, int flags,
                               char *dev_name, struct vfsmount *vmnt)
{
	struct block_device *bdev;
	struct ext2_sb *e2sb;
	struct ext2_block_group *e2bg;
	unsigned int blks_per_group, num_blk_group, num_blks;

	static bool ran_once = FALSE;
	if (!ran_once) {
		ran_once = TRUE;
		ext2_init();
	}
	bdev = get_bdev(dev_name);
	assert(bdev);
	/* Read the SB.  It's always at byte 1024 and 1024 bytes long.  Note we do
	 * not put the metablock (we pin it off the sb later).  Same with e2bg. */
	e2sb = (struct ext2_sb*)__ext2_get_metablock(bdev, 1, 1024);
	if (!(le16_to_cpu(e2sb->s_magic) == EXT2_SUPER_MAGIC)) {
		warn("EXT2 Not detected when it was expected!");
		return 0;
	}
	/* Read in the block group descriptor table.  Which block the BG table is on
	 * depends on the blocksize */
	unsigned int blksize = 1024 << le32_to_cpu(e2sb->s_log_block_size);
	e2bg = __ext2_get_metablock(bdev, blksize == 1024 ? 2 : 1, blksize);
	assert(e2bg);
	ext2_check_sb(e2sb, e2bg, FALSE);

	/* Now we build and init the VFS SB */
	struct super_block *sb = get_sb();
	sb->s_dev = 0;			/* what do we really want here? */
	sb->s_blocksize = blksize;
	/* max file size for a 1024 blocksize FS.  good enough for now (TODO) */
	sb->s_maxbytes = 17247252480;
	sb->s_type = &ext2_fs_type;
	sb->s_op = &ext2_s_op;
	sb->s_flags = flags;	/* from the disc too?  which flags are these? */
	sb->s_magic = EXT2_SUPER_MAGIC;
	sb->s_mount = vmnt;	/* Kref?  also in KFS */
	sb->s_syncing = FALSE;
	kref_get(&bdev->b_kref, 1);
	sb->s_bdev = bdev;
	strlcpy(sb->s_name, "EXT2", 32);
	sb->s_fs_info = kmalloc(sizeof(struct ext2_sb_info), 0);
	assert(sb->s_fs_info);
	/* store the in-memory copy of the disk SB and bg desc table */
	((struct ext2_sb_info*)sb->s_fs_info)->e2sb = e2sb;
	((struct ext2_sb_info*)sb->s_fs_info)->e2bg = e2bg;
	/* Precompute the number of BGs */
	num_blks = le32_to_cpu(e2sb->s_blocks_cnt);
	blks_per_group = le32_to_cpu(e2sb->s_blocks_per_group);
	((struct ext2_sb_info*)sb->s_fs_info)->nr_bgs = num_blks / blks_per_group +
	                                       (num_blks % blks_per_group ? 1 : 0);

	/* Final stages of initializing the sb, mostly FS-independent */
	init_sb(sb, vmnt, &ext2_d_op, EXT2_ROOT_INO, 0);

	printk("EXT2 superblock loaded\n");
	kref_put(&bdev->b_kref);
	return sb;
}

void ext2_kill_sb(struct super_block *sb)
{
	/* don't forget to kfree the s_fs_info and its two members */
	panic("Killing an EXT2 SB is not supported!");
}

/* Every FS must have a static FS Type, with which the VFS code can bootstrap */
struct fs_type ext2_fs_type = {"EXT2", 0, ext2_get_sb, ext2_kill_sb, {0, 0},
                               TAILQ_HEAD_INITIALIZER(ext2_fs_type.fs_supers)};

/* Page Map Operations */

/* Sets up the bidirectional mapping between the page and its buffer heads.  As
 * a future optimization, we could try and detect if all of the blocks are
 * contiguous (either before or after making them) and compact them to one BH.
 * Note there is an assumption that the file has at least one block in it. */
int ext2_mappage(struct page_map *pm, struct page *page)
{
	struct buffer_head *bh;
	struct inode *inode = (struct inode*)pm->pm_host;
	assert(!page->pg_private);		/* double check that we aren't bh-mapped */
	assert(inode->i_mapping == pm);	/* double check we are the inode for pm */
	struct block_device *bdev = inode->i_sb->s_bdev;
	unsigned int blk_per_pg = PGSIZE / inode->i_sb->s_blocksize;
	unsigned int sct_per_blk = inode->i_sb->s_blocksize / bdev->b_sector_sz;
	uint32_t ino_blk_num, fs_blk_num = 0, *fs_blk_slot;

	bh = kmem_cache_alloc(bh_kcache, 0);
	page->pg_private = bh;
	for (int i = 0; i < blk_per_pg; i++) {
		/* free_bh() can handle having a halfway aborted mappage() */
		if (!bh)
			return -ENOMEM;
		bh->bh_page = page;							/* weak ref */
		bh->bh_buffer = page2kva(page) + i * inode->i_sb->s_blocksize;
		bh->bh_flags = 0;							/* whatever... */
		bh->bh_bdev = bdev;							/* uncounted ref */
		/* compute the first sector of the FS block for the ith buf in the pg */
		ino_blk_num = page->pg_index * blk_per_pg + i;
		fs_blk_slot = ext2_lookup_inotable_slot(inode, ino_blk_num);
		/* If there isn't a block there, lets get one.  The previous fs_blk_num
		 * is our hint (or we have to compute one). */
		if (!*fs_blk_slot) {
			if (!fs_blk_num) {
				fs_blk_num = ext2_bgidx2block(inode->i_sb,
				                              ext2_inode2bg(inode), 0);
			}
			fs_blk_num = ext2_alloc_block(inode, fs_blk_num + 1);
			/* Link it, and dirty the inode indirect block */
			*fs_blk_slot = cpu_to_le32(fs_blk_num);
			ext2_dirty_metablock(inode->i_sb, fs_blk_slot);
			/* the block is still on disk, and we don't want its contents */
			bh->bh_flags = BH_NEEDS_ZEROED;			/* talking to readpage */
			/* update our num blocks, with 512B each "block" (ext2-style) */
			inode->i_blocks += inode->i_sb->s_blocksize >> 9;
		} else {	/* there is a block there already */
			fs_blk_num = *fs_blk_slot;
		}
		ext2_put_metablock(inode->i_sb, fs_blk_slot);
		bh->bh_sector = fs_blk_num * sct_per_blk;
		bh->bh_nr_sector = sct_per_blk;
		/* Stop if we're the last block in the page.  We could be going beyond
		 * the end of the file, in which case the next BHs will be zeroed. */
		if (i == blk_per_pg - 1) {
			bh->bh_next = 0;
			break;
		} else {
			/* get and link to the next BH. */
			bh->bh_next = kmem_cache_alloc(bh_kcache, 0);
			bh = bh->bh_next;
		}
	}
	return 0;
}

/* Fills page with its contents from its backing store file.  Note that we do
 * the zero padding here, instead of higher in the VFS.  Might change in the
 * future.  TODO: make this a block FS generic call. */
int ext2_readpage(struct page_map *pm, struct page *page)
{
	int retval;
	struct block_device *bdev = pm->pm_host->i_sb->s_bdev;
	struct buffer_head *bh;
	struct block_request *breq;
	void *eobh;

	atomic_or(&page->pg_flags, PG_BUFFER);
	retval = ext2_mappage(pm, page);
	if (retval)
		return retval;
	/* Build and submit the request */
	breq = kmem_cache_alloc(breq_kcache, 0);
	if (!breq)
		return -ENOMEM;
	breq->flags = BREQ_READ;
	breq->callback = generic_breq_done;
	breq->data = 0;
	sem_init_irqsave(&breq->sem, 0);
	breq->bhs = breq->local_bhs;
	breq->nr_bhs = 0;
	/* Pack the BH pointers in the block request */
	bh = (struct buffer_head*)page->pg_private;
	assert(bh);
	/* Either read the block in, or zero the buffer.  If we wanted to ensure no
	 * data is leaked after a crash, we'd write a 0 block too. */
	for (int i = 0; bh; bh = bh->bh_next) {
		if (!(bh->bh_flags & BH_NEEDS_ZEROED)) {
			breq->bhs[i] = bh;
			breq->nr_bhs++;
			i++;
		} else {
			memset(bh->bh_buffer, 0, pm->pm_host->i_sb->s_blocksize);
			bh->bh_flags |= BH_DIRTY;
			atomic_or(&bh->bh_page->pg_flags, PG_DIRTY);
		}
	}
	retval = bdev_submit_request(bdev, breq);
	assert(!retval);
	sleep_on_breq(breq);
	kmem_cache_free(breq_kcache, breq);
	/* zero out whatever is beyond the EOF.  we could do this by figuring out
	 * where the BHs end and zeroing from there, but I'd rather zero from where
	 * the file ends (which could be in the middle of an FS block */
	uintptr_t eof_off;
	eof_off = (pm->pm_host->i_size - page->pg_index * PGSIZE);
	eof_off = MIN(eof_off, PGSIZE) % PGSIZE;
	/* at this point, eof_off is the offset into the page of the EOF, or 0 */
	if (eof_off)
		memset(eof_off + page2kva(page), 0, PGSIZE - eof_off);
	/* Now the page is up to date */
	atomic_or(&page->pg_flags, PG_UPTODATE);
	/* Useful debugging.  Put one higher up if the page is not getting mapped */
	//print_pageinfo(page);
	return 0;
}

int ext2_writepage(struct page_map *pm, struct page *page)
{
	return -1;
}

/* Super Operations */

/* Creates and initializes a new inode.  FS specific, yet inode-generic fields
 * are filled in.  inode-specific fields are filled in in read_inode() based on
 * what's on the disk for a given i_no.  i_no and i_fop are 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.  The i_fop depends on the type of file
 * (file, directory, symlink, etc). */
struct inode *ext2_alloc_inode(struct super_block *sb)
{
	struct inode *inode = kmem_cache_alloc(inode_kcache, 0);
	memset(inode, 0, sizeof(struct inode));
	inode->i_op = &ext2_i_op;
	inode->i_pm.pm_op = &ext2_pm_op;
	return inode;
}

/* FS-specific clean up when an inode is dealloced.  this is just cleaning up
 * the in-memory version, and only the FS-specific parts.  whether or not the
 * inode is still on disc is irrelevant. */
void ext2_dealloc_inode(struct inode *inode)
{
	kmem_cache_free(ext2_i_kcache, inode->i_fs_info);
}

/* Returns a pointer within a metablock for the disk inode specified by inode.
 * Be sure to 'put' your reference (and/or dirty it). */
struct ext2_inode *ext2_get_diskinode(struct inode *inode)
{
	uint32_t my_bg_idx, ino_per_blk, my_ino_blk;
	struct ext2_sb_info *e2sbi = (struct ext2_sb_info*)inode->i_sb->s_fs_info;
	struct ext2_block_group *my_bg;
	struct ext2_inode *ino_tbl_chunk;

	assert(inode->i_ino);					/* ino == 0 is a bug */
	/* Need to compute the blockgroup and index of the requested inode */
	ino_per_blk = inode->i_sb->s_blocksize /
	              le16_to_cpu(e2sbi->e2sb->s_inode_size);
	my_bg_idx = ext2_inode2bgidx(inode);
	my_bg = ext2_inode2bg(inode);
	/* Figure out which FS block of the inode table we want and read in that
	 * chunk */
	my_ino_blk = le32_to_cpu(my_bg->bg_inode_table) + my_bg_idx / ino_per_blk;
	ino_tbl_chunk = ext2_get_metablock(inode->i_sb, my_ino_blk);
	return &ino_tbl_chunk[my_bg_idx % ino_per_blk];
}

/* reads the inode data on disk specified by inode->i_ino into the inode.
 * basically, it's a "make this inode the one for i_ino (i number)" */
void ext2_read_inode(struct inode *inode)
{
	struct ext2_inode *my_ino;
	my_ino = ext2_get_diskinode(inode);

	/* Have the disk inode now, let's put its info into the VFS inode: */
	inode->i_mode = le16_to_cpu(my_ino->i_mode);
	switch (inode->i_mode & __S_IFMT) {
		case (__S_IFDIR):
			inode->i_fop = &ext2_f_op_dir;
			break;
		case (__S_IFREG):
			inode->i_fop = &ext2_f_op_file;
			break;
		case (__S_IFLNK):
			inode->i_fop = &ext2_f_op_sym;
			break;
		case (__S_IFCHR):
		case (__S_IFBLK):
		default:
			inode->i_fop = &ext2_f_op_file;
			warn("[Calm British Accent] Look around you.  Unhandled filetype.");
	}
	inode->i_nlink = le16_to_cpu(my_ino->i_links_cnt);
	inode->i_uid = le16_to_cpu(my_ino->i_uid);
	inode->i_gid = le16_to_cpu(my_ino->i_gid);
	/* technically, for large F_REG, we should | with i_dir_acl */
	inode->i_size = le32_to_cpu(my_ino->i_size);
	inode->i_atime.tv_sec = le32_to_cpu(my_ino->i_atime);
	inode->i_atime.tv_nsec = 0;
	inode->i_mtime.tv_sec = le32_to_cpu(my_ino->i_mtime);
	inode->i_mtime.tv_nsec = 0;
	inode->i_ctime.tv_sec = le32_to_cpu(my_ino->i_ctime);
	inode->i_ctime.tv_nsec = 0;
	inode->i_blocks = le32_to_cpu(my_ino->i_blocks);
	inode->i_flags = le32_to_cpu(my_ino->i_flags);
	inode->i_socket = FALSE;		/* for now */
	/* Copy over the other inode stuff that isn't in the VFS inode.  For now,
	 * it's just the block pointers */
	inode->i_fs_info = kmem_cache_alloc(ext2_i_kcache, 0);
	struct ext2_i_info *e2ii = (struct ext2_i_info*)inode->i_fs_info;
	for (int i = 0; i < 15; i++)
		e2ii->i_block[i] = le32_to_cpu(my_ino->i_block[i]);
	/* TODO: (HASH) unused: inode->i_hash add to hash (saves on disc reading) */
	/* TODO: we could consider saving a pointer to the disk inode and pinning
	 * its buffer in memory, but for now we'll just free it. */
	ext2_put_metablock(inode->i_sb, my_ino);
}

/* called when an inode in memory is modified (journalling FS's care) */
void ext2_dirty_inode(struct inode *inode)
{
	// presumably we'll ext2_dirty_metablock(void *buffer) here
}

/* write the inode to disk (specifically, to inode inode->i_ino), synchronously
 * if we're asked to wait */
void ext2_write_inode(struct inode *inode, bool wait)
{
I_AM_HERE;
}

/* called when an inode is decref'd, to do any FS specific work */
void ext2_put_inode(struct inode *inode)
{
I_AM_HERE;
}

/* Unused for now, will get rid of this if inode_release is sufficient */
void ext2_drop_inode(struct inode *inode)
{
I_AM_HERE;
}

/* delete the inode from disk (all data) */
void ext2_delete_inode(struct inode *inode)
{
I_AM_HERE;
	// would remove from "disk" here
	/* TODO: give up our i_ino */
}

/* unmount and release the super block */
void ext2_put_super(struct super_block *sb)
{
	panic("Shazbot! Ext2 can't be unmounted yet!");
}

/* updates the on-disk SB with the in-memory SB */
void ext2_write_super(struct super_block *sb)
{
I_AM_HERE;
}

/* syncs FS metadata with the disc, synchronously if we're waiting.  this info
 * also includes anything pointed to by s_fs_info. */
int ext2_sync_fs(struct super_block *sb, bool wait)
{
I_AM_HERE;
	return 0;
}

/* remount the FS with the new flags */
int ext2_remount_fs(struct super_block *sb, int flags, char *data)
{
	warn("Ext2 will not remount.");
	return -1; // can't remount
}

/* interrupts a mount operation - used by NFS and friends */
void ext2_umount_begin(struct super_block *sb)
{
	panic("Cannot abort a Ext2 mount, and why would you?");
}

/* inode_operations */

/* Little helper, used for initializing new inodes for file-like objects (files,
 * symlinks, etc).  We pass the dentry, since we need to up it. */
static void ext2_init_inode(struct inode *dir, struct dentry *dentry)
{
#if 0
	struct inode *inode = dentry->d_inode;
	inode->i_ino = ext2_get_free_ino();
#endif
}

/* Initializes a new/empty disk inode, according to inode.  If you end up not
 * zeroing this stuff, be careful of endianness. */
static void ext2_init_diskinode(struct ext2_inode *e2i, struct inode *inode)
{
	assert(inode->i_size == 0);
	e2i->i_mode = cpu_to_le16(inode->i_mode);
	e2i->i_uid = cpu_to_le16(inode->i_uid);
	e2i->i_size = 0;
	e2i->i_atime = cpu_to_le32(inode->i_atime.tv_sec);
	e2i->i_ctime = cpu_to_le32(inode->i_ctime.tv_sec);
	e2i->i_mtime = cpu_to_le32(inode->i_mtime.tv_sec);
	e2i->i_dtime = 0;
	e2i->i_gid = cpu_to_le16(inode->i_gid);
	e2i->i_links_cnt = cpu_to_le16(inode->i_nlink);
	e2i->i_blocks = 0;
	e2i->i_flags = cpu_to_le32(inode->i_flags);
	e2i->i_osd1 = 0;
	e2i->i_generation = 0;
	e2i->i_file_acl = 0;
	e2i->i_dir_acl = 0;
	e2i->i_faddr = 0;
	for (int i = 0; i < 15; i++)
		e2i->i_block[i] = 0;
	for (int i = 0; i < 12; i++)
		e2i->i_osd2[i] = 0;
}

/* These should return true if foreach_dirent should stop working on the
 * dirents. */
typedef bool (*each_func_t) (struct ext2_dirent *dir_i, long a1, long a2,
                             long a3);

/* Loads the buffer and performs my_work on each dirent, stopping and returning
 * 0 if one of the calls succeeded, or returning the dir block num of what would
 * be the next dir block otherwise (aka, how many blocks we went through). */
static uint32_t ext2_foreach_dirent(struct inode *dir, each_func_t my_work,
                                    long a1, long a2, long a3)
{
	struct ext2_dirent *dir_buf, *dir_i;
	uint32_t dir_block = 0;
	dir_buf = ext2_get_ino_metablock(dir, dir_block++);
	dir_i = dir_buf;
	/* now we have the first block worth of dirents.  We'll get another block if
	 * dir_i hits a block boundary */
	for (unsigned int bytes = 0; bytes < dir->i_size; ) {
		/* On subsequent loops, we might need to advance to the next block.
		 * This is where a file abstraction for a dir might be easier. */
		if ((void*)dir_i >= (void*)dir_buf + dir->i_sb->s_blocksize) {
			ext2_put_metablock(dir->i_sb, dir_buf);
			dir_buf = ext2_get_ino_metablock(dir, dir_block++);
			dir_i = dir_buf;
			assert(dir_buf);
		}
		if (my_work(dir_i, a1, a2, a3)) {
			ext2_put_metablock(dir->i_sb, dir_buf);
			return 0;
		}
		/* Get ready for the next loop */
		bytes += dir_i->dir_reclen;
		dir_i = (void*)dir_i + dir_i->dir_reclen;
	}
	ext2_put_metablock(dir->i_sb, dir_buf);
	return dir_block;
}

/* Returns the actual length of a dirent, not just how far to the next entry.
 * If there is no inode, the entry is unused, and it has no length (as far as
 * users of this should care). */
static unsigned int ext2_dirent_len(struct ext2_dirent *e2dir)
{
	/* arguably, we don't need the le32_to_cpu */
	if (le32_to_cpu(e2dir->dir_inode))
		return ROUNDUP(e2dir->dir_namelen + 8, 4);		/* no such le8_to_cpu */
	else
		return 0;
}

/* Helper for writing the contents of a dentry to a disk dirent. Zeroes the
 * contents of the dirent so that we don't write random data to disk. */
static void ext2_write_dirent(struct ext2_dirent *e2dir, struct dentry *dentry,
                              unsigned int rec_len)
{
	memset(e2dir, 0, sizeof(*e2dir));
	e2dir->dir_inode = cpu_to_le32(dentry->d_inode->i_ino);
	e2dir->dir_reclen = cpu_to_le16(rec_len);
	e2dir->dir_namelen = dentry->d_name.len;
	switch (dentry->d_inode->i_mode & __S_IFMT) {
		case (__S_IFDIR):
			e2dir->dir_filetype = EXT2_FT_DIR;
			break;
		case (__S_IFREG):
			e2dir->dir_filetype = EXT2_FT_REG_FILE;
			break;
		case (__S_IFLNK):
			e2dir->dir_filetype = EXT2_FT_SYMLINK;
			break;
		case (__S_IFCHR):
			e2dir->dir_filetype = EXT2_FT_CHRDEV;
			break;
		case (__S_IFBLK):
			e2dir->dir_filetype = EXT2_FT_BLKDEV;
			break;
		case (__S_IFSOCK):
			e2dir->dir_filetype = EXT2_FT_SOCK;
			break;
		default:
			warn("[Calm British Accent] Look around you: Unknown filetype.");
			e2dir->dir_filetype = EXT2_FT_UNKNOWN;
	}
	assert(dentry->d_name.len <= 255);
	strlcpy((char*)e2dir->dir_name, dentry->d_name.name,
	        sizeof(e2dir->dir_name));
}

/* Helper for ext2_create().  This tries to squeeze a dirent in the slack space
 * after an existing dirent, returning TRUE if it succeeded (to break out). */
static bool create_each_func(struct ext2_dirent *dir_i, long a1, long a2,
                             long a3)
{
	struct dentry *dentry = (struct dentry*)a1;
	unsigned int our_rec_len = (unsigned int)a2;
	unsigned int mode = (unsigned int)a3;
	struct ext2_dirent *dir_new;
	unsigned int real_len = ext2_dirent_len(dir_i);
	/* How much room is available after this dir_i before the next one */
	unsigned int record_slack = le16_to_cpu(dir_i->dir_reclen) - real_len;
	/* TODO: Note that this technique will clobber any directory indexing.  They
	 * exist after the .. entry with an inode of 0.  Check the docs for
	 * specifics and think up a nice way to tell the diff between a reserved
	 * entry and an unused one, when inode == 0. */
	if (record_slack < our_rec_len)
		return FALSE;
	/* At this point, there is enough room for us.  Stick our new one in right
	 * after the real len, making sure our reclen goes to the old end.  Note
	 * that it is possible to have a real_len of 0 (an unused entry).  In this
	 * case, we just end up taking over the spot in the dir_blk.  Be sure to set
	 * dir_i's reclen before dir_new's (in case they are the same). */
	dir_new = ((void*)dir_i + real_len);
	dir_i->dir_reclen = cpu_to_le16(real_len);
	ext2_write_dirent(dir_new, dentry, record_slack);
	ext2_dirty_metablock(dentry->d_sb, dir_new);
	return TRUE;
}

/* Called when creating a new disk inode in dir associated with dentry.  We need
 * to fill out the i_ino, set the type, and do whatever else we need */
int ext2_create(struct inode *dir, struct dentry *dentry, int mode,
               struct nameidata *nd)
{
	struct inode *inode = dentry->d_inode;
	struct ext2_block_group *dir_bg = ext2_inode2bg(dir);
	struct ext2_inode *disk_inode;
	struct ext2_i_info *e2ii;
	uint32_t dir_block;
	unsigned int our_rec_len;
	struct ext2_dirent *new_dirent;
	/* Set basic inode stuff for files, get a disk inode, etc */
	SET_FTYPE(inode->i_mode, __S_IFREG);
	inode->i_fop = &ext2_f_op_file;
	inode->i_ino = ext2_alloc_diskinode(inode, dir_bg);
	/* Initialize disk inode (this will be different for short symlinks) */
	disk_inode = ext2_get_diskinode(inode);
	ext2_init_diskinode(disk_inode, inode);
	/* Initialize the e2ii (might get rid of this cache of block info) */
	inode->i_fs_info = kmem_cache_alloc(ext2_i_kcache, 0);
	e2ii = (struct ext2_i_info*)inode->i_fs_info;
	for (int i = 0; i < 15; i++)
		e2ii->i_block[i] = le32_to_cpu(disk_inode->i_block[i]);
	/* Dirty and put the disk inode */
	ext2_dirty_metablock(dentry->d_sb, disk_inode);
	ext2_put_metablock(dentry->d_sb, disk_inode);
	/* Insert it in the directory (make a dirent, might expand the dir too) */
	/* Note the disk dir_name is not null terminated */
	our_rec_len = ROUNDUP(8 + dentry->d_name.len, 4);
	assert(our_rec_len <= 8 + 256);
	/* Consider caching the start point for future dirent ops.  Or even using
	 * the indexed directory.... */
	dir_block = ext2_foreach_dirent(dir, create_each_func, (long)dentry,
	                                (long)our_rec_len, (long)mode);
	/* If this returned a block number, we didn't find room in any of the
	 * existing directory blocks, so we need to make a new one, stick it in the
	 * dir inode, and stick our dirent at the beginning.  The reclen is the
	 * whole blocksize (since it's the last entry in this block) */
	if (dir_block) {
		new_dirent = ext2_get_ino_metablock(dir, dir_block);
		ext2_write_dirent(new_dirent, dentry, dentry->d_sb->s_blocksize);
		ext2_dirty_metablock(dentry->d_sb, new_dirent);
		ext2_put_metablock(dentry->d_sb, new_dirent);
	}
	return 0;
}

/* If we match, this loads the inode for the dentry and returns true (so we
 * break out) */
static bool lookup_each_func(struct ext2_dirent *dir_i, long a1, long a2,
                             long a3)
{
	struct dentry *dentry = (struct dentry*)a1;
	/* Test if we're the one (TODO: use d_compare).  Note, dir_name is not
	 * null terminated, hence the && test. */
	if (!strncmp((char*)dir_i->dir_name, dentry->d_name.name,
	             dir_i->dir_namelen) &&
	            (dentry->d_name.name[dir_i->dir_namelen] == '\0')) {
		load_inode(dentry, (long)le32_to_cpu(dir_i->dir_inode));
		/* TODO: (HASH) add dentry to dcache (maybe the caller should) */
		return TRUE;
	}
	return FALSE;
}

/* Searches the directory for the filename in the dentry, filling in the dentry
 * with the FS specific info of this file.  If it succeeds, it will pass back
 * the *dentry you should use (which might be the same as the one you passed in).
 * If this fails, it will return 0, but not free the memory of "dentry."
 *
 * Callers, make sure you alloc and fill out the name parts of the dentry.  We
 * don't currently use the ND.  Might remove it in the future.  */
struct dentry *ext2_lookup(struct inode *dir, struct dentry *dentry,
                           struct nameidata *nd)
{
	assert(S_ISDIR(dir->i_mode));
	struct ext2_dirent *dir_buf, *dir_i;
	if (!ext2_foreach_dirent(dir, lookup_each_func, (long)dentry, 0, 0))
		return dentry;
	printd("EXT2: Not Found, %s\n", dentry->d_name.name);
	return 0;
}

/* Hard link to old_dentry in directory dir with a name specified by new_dentry.
 * At the very least, set the new_dentry's FS-specific fields. */
int ext2_link(struct dentry *old_dentry, struct inode *dir,
             struct dentry *new_dentry)
{
I_AM_HERE;
	assert(new_dentry->d_op = &ext2_d_op);
	return 0;
}

/* Removes the link from the dentry in the directory */
int ext2_unlink(struct inode *dir, struct dentry *dentry)
{
I_AM_HERE;
	return 0;
}

/* Creates a new inode for a symlink dir, linking to / containing the name
 * symname.  dentry is the controlling dentry of the inode. */
int ext2_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
{
I_AM_HERE;
	#if 0
	struct inode *inode = dentry->d_inode;
	SET_FTYPE(inode->i_mode, __S_IFLNK);
	inode->i_fop = &ext2_f_op_sym;
	strlcpy(string, symname, len + 1);
	#endif
	return 0;
}

/* Called when creating a new inode for a directory associated with dentry in
 * dir with the given mode.  Note, we might (later) need to track subdirs within
 * the parent inode, like we do with regular files.  I'd rather not, so we'll
 * see if we need it. */
int ext2_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
I_AM_HERE;
	#if 0
	struct inode *inode = dentry->d_inode;
	inode->i_ino = ext2_get_free_ino();
	SET_FTYPE(inode->i_mode, __S_IFDIR);
	inode->i_fop = &ext2_f_op_dir;
	#endif
	return 0;
}

/* Removes from dir the directory 'dentry.'  Ext2 doesn't store anything in the
 * inode for which children it has.  It probably should, but since everything is
 * pinned, it just relies on the dentry connections. */
int ext2_rmdir(struct inode *dir, struct dentry *dentry)
{
I_AM_HERE;
	return 0;
}

/* Used to make a generic file, based on the type and the major/minor numbers
 * (in rdev), with the given mode.  As with others, this creates a new disk
 * inode for the file */
int ext2_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t rdev)
{
I_AM_HERE;
	return -1;
}

/* Moves old_dentry from old_dir to new_dentry in new_dir */
int ext2_rename(struct inode *old_dir, struct dentry *old_dentry,
               struct inode *new_dir, struct dentry *new_dentry)
{
I_AM_HERE;
	return -1;
}

/* Returns the char* for the symname for the given dentry.  The VFS code that
 * calls this for real FS's might assume it's already read in, so if the char *
 * isn't already in memory, we'd need to read it in here.  Regarding the char*
 * storage, the char* only will last as long as the dentry and inode are in
 * memory. */
char *ext2_readlink(struct dentry *dentry)
{
I_AM_HERE;
	struct inode *inode = dentry->d_inode;
	if (!S_ISLNK(inode->i_mode))
		return 0;
	return 0;
}

/* Modifies the size of the file of inode to whatever its i_size is set to */
void ext2_truncate(struct inode *inode)
{
}

/* Checks whether the the access mode is allowed for the file belonging to the
 * inode.  Implies that the permissions are on the file, and not the hardlink */
int ext2_permission(struct inode *inode, int mode, struct nameidata *nd)
{
	return -1;
}


/* dentry_operations */
/* Determines if the dentry is still valid before using it to translate a path.
 * Network FS's need to deal with this. */
int ext2_d_revalidate(struct dentry *dir, struct nameidata *nd)
{ // default, nothing
	return -1;
}

/* Compares name1 and name2.  name1 should be a member of dir. */
int ext2_d_compare(struct dentry *dir, struct qstr *name1, struct qstr *name2)
{ // default, string comp (case sensitive)
	return -1;
}

/* Called when the last ref is deleted (refcnt == 0) */
int ext2_d_delete(struct dentry *dentry)
{ // default, nothin
	return -1;
}

/* Called when it's about to be slab-freed */
int ext2_d_release(struct dentry *dentry)
{
	return -1;
}

/* Called when the dentry loses it's inode (becomes "negative") */
void ext2_d_iput(struct dentry *dentry, struct inode *inode)
{ // default, call i_put to release the inode object
}


/* file_operations */

/* Updates the file pointer.  TODO: think about locking, and putting this in the
 * VFS. */
#include <syscall.h>	/* just for set_errno, may go away later */
int ext2_llseek(struct file *file, off64_t offset, off64_t *ret, int whence)
{
	off64_t temp_off = 0;
	switch (whence) {
		case SEEK_SET:
			temp_off = offset;
			break;
		case SEEK_CUR:
			temp_off = file->f_pos + offset;
			break;
		case SEEK_END:
			temp_off = file->f_dentry->d_inode->i_size + offset;
			break;
		default:
			set_errno(EINVAL);
			warn("Unknown 'whence' in llseek()!\n");
			return -1;
	}
	file->f_pos = temp_off;
	*ret = temp_off;
	return 0;
}

/* Fills in the next directory entry (dirent), starting with d_off.  Like with
 * read and write, there will be issues with userspace and the *dirent buf.
 * TODO: (UMEM) */
int ext2_readdir(struct file *dir, struct dirent *dirent)
{
	void *blk_buf;
	/* Not enough data at the end of the directory */
	if (dir->f_dentry->d_inode->i_size < dirent->d_off + 8)
		return -ENOENT;
	/* Figure out which block we need to read in for dirent->d_off */
	int block = dirent->d_off / dir->f_dentry->d_sb->s_blocksize;
	blk_buf = ext2_get_ino_metablock(dir->f_dentry->d_inode, block);
	assert(blk_buf);
	off64_t f_off = dirent->d_off % dir->f_dentry->d_sb->s_blocksize;
	/* Copy out the dirent info */
	struct ext2_dirent *e2dir = (struct ext2_dirent*)(blk_buf + f_off);
	dirent->d_ino = le32_to_cpu(e2dir->dir_inode);
	dirent->d_off += le16_to_cpu(e2dir->dir_reclen);
	if (dir->f_dentry->d_inode->i_size < dirent->d_off)
		panic("Something is jacked with the dirent going beyond the dir/file");
	/* note, dir_namelen doesn't include the \0 */
	dirent->d_reclen = e2dir->dir_namelen;
	assert(e2dir->dir_namelen <= MAX_FILENAME_SZ);
	strlcpy(dirent->d_name, (char*)e2dir->dir_name, e2dir->dir_namelen + 1);
	ext2_put_metablock(dir->f_dentry->d_sb, blk_buf);

	/* At the end of the directory, sort of.  ext2 often preallocates blocks, so
	 * this will cause us to walk along til the end, which isn't quite right. */
	if (dir->f_dentry->d_inode->i_size == dirent->d_off)
		return 0;
	if (dir->f_dentry->d_inode->i_size < dirent->d_off) {
		warn("Issues reaching the end of an ext2 directory!");
		return 0;
	}
	return 1;							/* normal success for readdir */
}

/* This is called when a VMR is mapping a particular file.  The FS needs to do
 * whatever it needs so that faults can be handled by read_page(), and handle all
 * of the cases of MAP_SHARED, MAP_PRIVATE, whatever.  It also needs to ensure
 * the file is not being mmaped in a way that conflicts with the manner in which
 * the file was opened or the file type. */
int ext2_mmap(struct file *file, struct vm_region *vmr)
{
	if (S_ISREG(file->f_dentry->d_inode->i_mode))
		return 0;
	return -1;
}

/* Called by the VFS while opening the file, which corresponds to inode,  for
 * the FS to do whatever it needs. */
int ext2_open(struct inode *inode, struct file *file)
{
	/* TODO: check to make sure the file is openable, and maybe do some checks
	 * for the open mode (like did we want to truncate, append, etc) */
	return 0;
}

/* Called when a file descriptor is closed. */
int ext2_flush(struct file *file)
{
I_AM_HERE;
	return -1;
}

/* Called when the file is about to be closed (file obj freed) */
int ext2_release(struct inode *inode, struct file *file)
{
	return 0;
}

/* Flushes the file's dirty contents to disc */
int ext2_fsync(struct file *file, struct dentry *dentry, int datasync)
{
	return -1;
}

/* Traditionally, sleeps until there is file activity.  We probably won't
 * support this, or we'll handle it differently. */
unsigned int ext2_poll(struct file *file, struct poll_table_struct *poll_table)
{
	return -1;
}

/* Reads count bytes from a file, starting from (and modifiying) offset, and
 * putting the bytes into buffers described by vector */
ssize_t ext2_readv(struct file *file, const struct iovec *vector,
                  unsigned long count, off64_t *offset)
{
	return -1;
}

/* Writes count bytes to a file, starting from (and modifiying) offset, and
 * taking the bytes from buffers described by vector */
ssize_t ext2_writev(struct file *file, const struct iovec *vector,
                  unsigned long count, off64_t *offset)
{
	return -1;
}

/* Write the contents of file to the page.  Will sort the params later */
ssize_t ext2_sendpage(struct file *file, struct page *page, int offset,
                     size_t size, off64_t pos, int more)
{
	return -1;
}

/* Checks random FS flags.  Used by NFS. */
int ext2_check_flags(int flags)
{ // default, nothing
	return -1;
}

/* Redeclaration and initialization of the FS ops structures */
struct page_map_operations ext2_pm_op = {
	ext2_readpage,
	ext2_writepage,
};

struct super_operations ext2_s_op = {
	ext2_alloc_inode,
	ext2_dealloc_inode,
	ext2_read_inode,
	ext2_dirty_inode,
	ext2_write_inode,
	ext2_put_inode,
	ext2_drop_inode,
	ext2_delete_inode,
	ext2_put_super,
	ext2_write_super,
	ext2_sync_fs,
	ext2_remount_fs,
	ext2_umount_begin,
};

struct inode_operations ext2_i_op = {
	ext2_create,
	ext2_lookup,
	ext2_link,
	ext2_unlink,
	ext2_symlink,
	ext2_mkdir,
	ext2_rmdir,
	ext2_mknod,
	ext2_rename,
	ext2_readlink,
	ext2_truncate,
	ext2_permission,
};

struct dentry_operations ext2_d_op = {
	ext2_d_revalidate,
	generic_dentry_hash,
	ext2_d_compare,
	ext2_d_delete,
	ext2_d_release,
	ext2_d_iput,
};

struct file_operations ext2_f_op_file = {
	ext2_llseek,
	generic_file_read,
	generic_file_write,
	ext2_readdir,
	ext2_mmap,
	ext2_open,
	ext2_flush,
	ext2_release,
	ext2_fsync,
	ext2_poll,
	ext2_readv,
	ext2_writev,
	ext2_sendpage,
	ext2_check_flags,
};

struct file_operations ext2_f_op_dir = {
	ext2_llseek,
	generic_dir_read,
	0,
	ext2_readdir,
	ext2_mmap,
	ext2_open,
	ext2_flush,
	ext2_release,
	ext2_fsync,
	ext2_poll,
	ext2_readv,
	ext2_writev,
	ext2_sendpage,
	ext2_check_flags,
};

struct file_operations ext2_f_op_sym = {
	ext2_llseek,
	generic_file_read,
	generic_file_write,
	ext2_readdir,
	ext2_mmap,
	ext2_open,
	ext2_flush,
	ext2_release,
	ext2_fsync,
	ext2_poll,
	ext2_readv,
	ext2_writev,
	ext2_sendpage,
	ext2_check_flags,
};