The write range may not be sector-aligned, for example:
|--------|--------| <- write range, sector-unaligned, size: 2blocks
|--------|--------|--------| <- correct lock range, size: 3blocks
But according to the old code, we used the size of write range to calculate
the lock range directly, not considered the offset, we would get a wrong lock
range:
|--------|--------| <- write range, sector-unaligned, size: 2blocks
|--------|--------| <- wrong lock range, size: 2blocks
And besides that, the old code also had the same problem when calculating
the real write size. Correct them.
Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
---
fs/btrfs/file.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 0165b86..56f8a07 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1397,7 +1397,7 @@ static noinline int check_can_nocow(struct inode *inode, loff_t pos,
int ret;
lockstart = round_down(pos, root->sectorsize);
- lockend = lockstart + round_up(*write_bytes, root->sectorsize) - 1;
+ lockend = round_up(pos + *write_bytes, root->sectorsize) - 1;
while (1) {
lock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);
@@ -1420,7 +1420,8 @@ static noinline int check_can_nocow(struct inode *inode, loff_t pos,
EXTENT_DIRTY | EXTENT_DELALLOC |
EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG, 0, 0,
NULL, GFP_NOFS);
- *write_bytes = min_t(size_t, *write_bytes, num_bytes);
+ *write_bytes = min_t(size_t, *write_bytes ,
+ num_bytes - pos + lockstart);
}
unlock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);
--
1.8.1.4
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