Qu Wenruo
2014-Aug-08 05:06 UTC
[PATCH] btrfs: Use right extent length when inserting overlap extent map.
When current btrfs finds that a new extent map is going to be insereted
but failed with -EEXIST, it will try again to insert the extent map
but with the length of sectorsize.
This is OK if we don't enable 'no-holes' feature since all extent
space
is continuous, we will not go into the not found->insert routine.
But if we enable 'no-holes' feature, it will make things out of control.
e.g. in 4K sectorsize, we pass the following args to btrfs_get_extent():
btrfs_get_extent() args: start: 27874 len 4100
28672 27874 28672 27874+4100 32768
|-----------------------|
|---------hole--------------------|---------data----------|
1) not found and insert
Since no extent map containing the range, btrfs_get_extent() will go
into the not_found and insert routine, which will try to insert the
extent map (27874, 27847 + 4100).
2) first overlap
But it overlaps with (28672, 32768) extent, so -EEXIST will be returned
by add_extent_mapping().
3) retry but still overlap
After catching the -EEXIST, then btrfs_get_extent() will try insert it
again but with 4K length, which still overlaps, so -EEXIST will be
returned.
This makes the following patch fail to punch hole.
d77815461f047e561f77a07754ae923ade597d4e btrfs: Avoid trucating page or punching
hole in a already existed hole.
This patch will use the right length, which is the (exsisting->start -
em->start) to insert, making the above patch works in 'no-holes'
mode.
Also, some small code style problems in above patch is fixed too.
Reported-by: Filipe David Manana <fdmanana@gmail.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
fs/btrfs/file.c | 4 ++--
fs/btrfs/inode.c | 7 +++----
2 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 1f2b99c..6eb71e6 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2240,7 +2240,7 @@ static int btrfs_punch_hole(struct inode *inode, loff_t
offset, loff_t len)
goto out_only_mutex;
}
- lockstart = round_up(offset , BTRFS_I(inode)->root->sectorsize);
+ lockstart = round_up(offset, BTRFS_I(inode)->root->sectorsize);
lockend = round_down(offset + len,
BTRFS_I(inode)->root->sectorsize) - 1;
same_page = ((offset >> PAGE_CACHE_SHIFT) =@@ -2301,7 +2301,7 @@ static
int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
tail_start + tail_len, 0, 1);
if (ret)
goto out_only_mutex;
- }
+ }
}
}
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3668048..391dcd3 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6085,14 +6085,14 @@ out_fail:
static int merge_extent_mapping(struct extent_map_tree *em_tree,
struct extent_map *existing,
struct extent_map *em,
- u64 map_start, u64 map_len)
+ u64 map_start)
{
u64 start_diff;
BUG_ON(map_start < em->start || map_start >= extent_map_end(em));
start_diff = map_start - em->start;
em->start = map_start;
- em->len = map_len;
+ em->len = existing->start - em->start;
if (em->block_start < EXTENT_MAP_LAST_BYTE &&
!test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
em->block_start += start_diff;
@@ -6378,8 +6378,7 @@ insert:
em->len);
if (existing) {
err = merge_extent_mapping(em_tree, existing,
- em, start,
- root->sectorsize);
+ em, start);
free_extent_map(existing);
if (err) {
free_extent_map(em);
--
2.0.4
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