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Btrfs: fix defrag regression 

If a file has 3 small extents:

| ext1 | ext2 | ext3 |

Running "btrfs fi defrag" will only defrag the last two extents, if those
extent mappings hasn't been read into memory from disk.

This bug was introduced by commit 17ce6ef8d7
("Btrfs: add a check to decide if we should defrag the range")

The cause is, that commit looked into previous and next extents using
lookup_extent_mapping() only.

While at it, remove the code that checks the previous extent, since
it's sufficient to check the next extent.

Signed-off-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Li Zefan 2012-06-11 16:03:35 +08:00 committed by Chris Mason
parent 7ddf5a42d3
commit 6c282eb40e
1 changed files with 51 additions and 50 deletions
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101
fs/btrfs/ioctl.c
View File

@ -786,48 +786,12 @@ none:
return -ENOENT;
}
/*
* Validaty check of prev em and next em:
* 1) no prev/next em
* 2) prev/next em is an hole/inline extent
*/
static int check_adjacent_extents(struct inode *inode, struct extent_map *em)
static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
{
struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
struct extent_map *prev = NULL, *next = NULL;
int ret = 0;
read_lock(&em_tree->lock);
prev = lookup_extent_mapping(em_tree, em->start - 1, (u64)-1);
next = lookup_extent_mapping(em_tree, em->start + em->len, (u64)-1);
read_unlock(&em_tree->lock);
if ((!prev || prev->block_start >= EXTENT_MAP_LAST_BYTE) &&
(!next || next->block_start >= EXTENT_MAP_LAST_BYTE))
ret = 1;
free_extent_map(prev);
free_extent_map(next);
return ret;
}
static int should_defrag_range(struct inode *inode, u64 start, u64 len,
int thresh, u64 *last_len, u64 *skip,
u64 *defrag_end)
{
struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
struct extent_map *em = NULL;
struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
int ret = 1;
/*
* make sure that once we start defragging an extent, we keep on
* defragging it
*/
if (start < *defrag_end)
return 1;
*skip = 0;
struct extent_map *em;
u64 len = PAGE_CACHE_SIZE;
/*
* hopefully we have this extent in the tree already, try without
@ -844,27 +808,64 @@ static int should_defrag_range(struct inode *inode, u64 start, u64 len,
unlock_extent(io_tree, start, start + len - 1);
if (IS_ERR(em))
return 0;
return NULL;
}
return em;
}
static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em)
{
struct extent_map *next;
bool ret = true;
/* this is the last extent */
if (em->start + em->len >= i_size_read(inode))
return false;
next = defrag_lookup_extent(inode, em->start + em->len);
if (!next || next->block_start >= EXTENT_MAP_LAST_BYTE)
ret = false;
free_extent_map(next);
return ret;
}
static int should_defrag_range(struct inode *inode, u64 start, int thresh,
u64 *last_len, u64 *skip, u64 *defrag_end)
{
struct extent_map *em;
int ret = 1;
bool next_mergeable = true;
/*
* make sure that once we start defragging an extent, we keep on
* defragging it
*/
if (start < *defrag_end)
return 1;
*skip = 0;
em = defrag_lookup_extent(inode, start);
if (!em)
return 0;
/* this will cover holes, and inline extents */
if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
ret = 0;
goto out;
}
/* If we have nothing to merge with us, just skip. */
if (check_adjacent_extents(inode, em)) {
ret = 0;
goto out;
}
next_mergeable = defrag_check_next_extent(inode, em);
/*
* we hit a real extent, if it is big don't bother defragging it again
* we hit a real extent, if it is big or the next extent is not a
* real extent, don't bother defragging it
*/
if ((*last_len == 0 || *last_len >= thresh) && em->len >= thresh)
if ((*last_len == 0 || *last_len >= thresh) &&
(em->len >= thresh || !next_mergeable))
ret = 0;
out:
/*
* last_len ends up being a counter of how many bytes we've defragged.
@ -1143,8 +1144,8 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
break;
if (!should_defrag_range(inode, (u64)i << PAGE_CACHE_SHIFT,
PAGE_CACHE_SIZE, extent_thresh,
&last_len, &skip, &defrag_end)) {
extent_thresh, &last_len, &skip,
&defrag_end)) {
unsigned long next;
/*
* the should_defrag function tells us how much to skip