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Btrfs: fix fiemap bugs with delalloc
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The Btrfs fiemap code wasn't properly returning delalloc extents,
so applications that trust fiemap to decide if there are holes in the
file see holes instead of delalloc.

This reworks the btrfs fiemap code, adding a get_extent helper that
searches for delalloc ranges and also adding a helper for extent_fiemap
that skips past holes in the file.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
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Chris Mason committed Feb 23, 2011
1 parent fb01aa8 commit ec29ed5
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Showing 3 changed files with 224 additions and 42 deletions.
138 changes: 99 additions & 39 deletions fs/btrfs/extent_io.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1433,12 +1433,13 @@ int extent_clear_unlock_delalloc(struct inode *inode,
*/
u64 count_range_bits(struct extent_io_tree *tree,
u64 *start, u64 search_end, u64 max_bytes,
unsigned long bits)
unsigned long bits, int contig)
{
struct rb_node *node;
struct extent_state *state;
u64 cur_start = *start;
u64 total_bytes = 0;
u64 last = 0;
int found = 0;

if (search_end <= cur_start) {
Expand All @@ -1463,7 +1464,9 @@ u64 count_range_bits(struct extent_io_tree *tree,
state = rb_entry(node, struct extent_state, rb_node);
if (state->start > search_end)
break;
if (state->end >= cur_start && (state->state & bits)) {
if (contig && found && state->start > last + 1)
break;
if (state->end >= cur_start && (state->state & bits) == bits) {
total_bytes += min(search_end, state->end) + 1 -
max(cur_start, state->start);
if (total_bytes >= max_bytes)
Expand All @@ -1472,6 +1475,9 @@ u64 count_range_bits(struct extent_io_tree *tree,
*start = state->start;
found = 1;
}
last = state->end;
} else if (contig && found) {
break;
}
node = rb_next(node);
if (!node)
Expand Down Expand Up @@ -2912,6 +2918,46 @@ sector_t extent_bmap(struct address_space *mapping, sector_t iblock,
return sector;
}

/*
* helper function for fiemap, which doesn't want to see any holes.
* This maps until we find something past 'last'
*/
static struct extent_map *get_extent_skip_holes(struct inode *inode,
u64 offset,
u64 last,
get_extent_t *get_extent)
{
u64 sectorsize = BTRFS_I(inode)->root->sectorsize;
struct extent_map *em;
u64 len;

if (offset >= last)
return NULL;

while(1) {
len = last - offset;
if (len == 0)
break;
len = (len + sectorsize - 1) & ~(sectorsize - 1);
em = get_extent(inode, NULL, 0, offset, len, 0);
if (!em || IS_ERR(em))
return em;

/* if this isn't a hole return it */
if (!test_bit(EXTENT_FLAG_VACANCY, &em->flags) &&
em->block_start != EXTENT_MAP_HOLE) {
return em;
}

/* this is a hole, advance to the next extent */
offset = extent_map_end(em);
free_extent_map(em);
if (offset >= last)
break;
}
return NULL;
}

int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
__u64 start, __u64 len, get_extent_t *get_extent)
{
Expand All @@ -2921,16 +2967,19 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
u32 flags = 0;
u32 found_type;
u64 last;
u64 last_for_get_extent = 0;
u64 disko = 0;
u64 isize = i_size_read(inode);
struct btrfs_key found_key;
struct extent_map *em = NULL;
struct extent_state *cached_state = NULL;
struct btrfs_path *path;
struct btrfs_file_extent_item *item;
int end = 0;
u64 em_start = 0, em_len = 0;
u64 em_start = 0;
u64 em_len = 0;
u64 em_end = 0;
unsigned long emflags;
int hole = 0;

if (len == 0)
return -EINVAL;
Expand All @@ -2940,6 +2989,10 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
return -ENOMEM;
path->leave_spinning = 1;

/*
* lookup the last file extent. We're not using i_size here
* because there might be preallocation past i_size
*/
ret = btrfs_lookup_file_extent(NULL, BTRFS_I(inode)->root,
path, inode->i_ino, -1, 0);
if (ret < 0) {
Expand All @@ -2953,18 +3006,38 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
found_type = btrfs_key_type(&found_key);

/* No extents, just return */
/* No extents, but there might be delalloc bits */
if (found_key.objectid != inode->i_ino ||
found_type != BTRFS_EXTENT_DATA_KEY) {
btrfs_free_path(path);
return 0;
/* have to trust i_size as the end */
last = (u64)-1;
last_for_get_extent = isize;
} else {
/*
* remember the start of the last extent. There are a
* bunch of different factors that go into the length of the
* extent, so its much less complex to remember where it started
*/
last = found_key.offset;
last_for_get_extent = last + 1;
}
last = found_key.offset;
btrfs_free_path(path);

/*
* we might have some extents allocated but more delalloc past those
* extents. so, we trust isize unless the start of the last extent is
* beyond isize
*/
if (last < isize) {
last = (u64)-1;
last_for_get_extent = isize;
}

lock_extent_bits(&BTRFS_I(inode)->io_tree, start, start + len, 0,
&cached_state, GFP_NOFS);
em = get_extent(inode, NULL, 0, off, max - off, 0);

em = get_extent_skip_holes(inode, off, last_for_get_extent,
get_extent);
if (!em)
goto out;
if (IS_ERR(em)) {
Expand All @@ -2973,19 +3046,14 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
}

while (!end) {
hole = 0;
off = em->start + em->len;
off = extent_map_end(em);
if (off >= max)
end = 1;

if (em->block_start == EXTENT_MAP_HOLE) {
hole = 1;
goto next;
}

em_start = em->start;
em_len = em->len;

em_end = extent_map_end(em);
emflags = em->flags;
disko = 0;
flags = 0;

Expand All @@ -3004,37 +3072,29 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
flags |= FIEMAP_EXTENT_ENCODED;

next:
emflags = em->flags;
free_extent_map(em);
em = NULL;
if (!end) {
em = get_extent(inode, NULL, 0, off, max - off, 0);
if (!em)
goto out;
if (IS_ERR(em)) {
ret = PTR_ERR(em);
goto out;
}
emflags = em->flags;
}

if (test_bit(EXTENT_FLAG_VACANCY, &emflags)) {
if ((em_start >= last) || em_len == (u64)-1 ||
(last == (u64)-1 && isize <= em_end)) {
flags |= FIEMAP_EXTENT_LAST;
end = 1;
}

if (em_start == last) {
/* now scan forward to see if this is really the last extent. */
em = get_extent_skip_holes(inode, off, last_for_get_extent,
get_extent);
if (IS_ERR(em)) {
ret = PTR_ERR(em);
goto out;
}
if (!em) {
flags |= FIEMAP_EXTENT_LAST;
end = 1;
}

if (!hole) {
ret = fiemap_fill_next_extent(fieinfo, em_start, disko,
em_len, flags);
if (ret)
goto out_free;
}
ret = fiemap_fill_next_extent(fieinfo, em_start, disko,
em_len, flags);
if (ret)
goto out_free;
}
out_free:
free_extent_map(em);
Expand Down
2 changes: 1 addition & 1 deletion fs/btrfs/extent_io.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -191,7 +191,7 @@ void extent_io_exit(void);

u64 count_range_bits(struct extent_io_tree *tree,
u64 *start, u64 search_end,
u64 max_bytes, unsigned long bits);
u64 max_bytes, unsigned long bits, int contig);

void free_extent_state(struct extent_state *state);
int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
Expand Down
126 changes: 124 additions & 2 deletions fs/btrfs/inode.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1913,7 +1913,7 @@ static int btrfs_clean_io_failures(struct inode *inode, u64 start)

private = 0;
if (count_range_bits(&BTRFS_I(inode)->io_failure_tree, &private,
(u64)-1, 1, EXTENT_DIRTY)) {
(u64)-1, 1, EXTENT_DIRTY, 0)) {
ret = get_state_private(&BTRFS_I(inode)->io_failure_tree,
start, &private_failure);
if (ret == 0) {
Expand Down Expand Up @@ -5282,6 +5282,128 @@ struct extent_map *btrfs_get_extent(struct inode *inode, struct page *page,
return em;
}

struct extent_map *btrfs_get_extent_fiemap(struct inode *inode, struct page *page,
size_t pg_offset, u64 start, u64 len,
int create)
{
struct extent_map *em;
struct extent_map *hole_em = NULL;
u64 range_start = start;
u64 end;
u64 found;
u64 found_end;
int err = 0;

em = btrfs_get_extent(inode, page, pg_offset, start, len, create);
if (IS_ERR(em))
return em;
if (em) {
/*
* if our em maps to a hole, there might
* actually be delalloc bytes behind it
*/
if (em->block_start != EXTENT_MAP_HOLE)
return em;
else
hole_em = em;
}

/* check to see if we've wrapped (len == -1 or similar) */
end = start + len;
if (end < start)
end = (u64)-1;
else
end -= 1;

em = NULL;

/* ok, we didn't find anything, lets look for delalloc */
found = count_range_bits(&BTRFS_I(inode)->io_tree, &range_start,
end, len, EXTENT_DELALLOC, 1);
found_end = range_start + found;
if (found_end < range_start)
found_end = (u64)-1;

/*
* we didn't find anything useful, return
* the original results from get_extent()
*/
if (range_start > end || found_end <= start) {
em = hole_em;
hole_em = NULL;
goto out;
}

/* adjust the range_start to make sure it doesn't
* go backwards from the start they passed in
*/
range_start = max(start,range_start);
found = found_end - range_start;

if (found > 0) {
u64 hole_start = start;
u64 hole_len = len;

em = alloc_extent_map(GFP_NOFS);
if (!em) {
err = -ENOMEM;
goto out;
}
/*
* when btrfs_get_extent can't find anything it
* returns one huge hole
*
* make sure what it found really fits our range, and
* adjust to make sure it is based on the start from
* the caller
*/
if (hole_em) {
u64 calc_end = extent_map_end(hole_em);

if (calc_end <= start || (hole_em->start > end)) {
free_extent_map(hole_em);
hole_em = NULL;
} else {
hole_start = max(hole_em->start, start);
hole_len = calc_end - hole_start;
}
}
em->bdev = NULL;
if (hole_em && range_start > hole_start) {
/* our hole starts before our delalloc, so we
* have to return just the parts of the hole
* that go until the delalloc starts
*/
em->len = min(hole_len,
range_start - hole_start);
em->start = hole_start;
em->orig_start = hole_start;
/*
* don't adjust block start at all,
* it is fixed at EXTENT_MAP_HOLE
*/
em->block_start = hole_em->block_start;
em->block_len = hole_len;
} else {
em->start = range_start;
em->len = found;
em->orig_start = range_start;
em->block_start = EXTENT_MAP_DELALLOC;
em->block_len = found;
}
} else if (hole_em) {
return hole_em;
}
out:

free_extent_map(hole_em);
if (err) {
free_extent_map(em);
return ERR_PTR(err);
}
return em;
}

static struct extent_map *btrfs_new_extent_direct(struct inode *inode,
u64 start, u64 len)
{
Expand Down Expand Up @@ -6104,7 +6226,7 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
__u64 start, __u64 len)
{
return extent_fiemap(inode, fieinfo, start, len, btrfs_get_extent);
return extent_fiemap(inode, fieinfo, start, len, btrfs_get_extent_fiemap);
}

int btrfs_readpage(struct file *file, struct page *page)
Expand Down

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