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Btrfs: fix wrong lock range and write size in check_can_nocow()

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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@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
This commit is contained in:
Miao Xie 2014-02-27 13:58:04 +08:00 committed by Josef Bacik
parent 9c9ca00bd3
commit c933956ddf
1 changed files with 3 additions and 2 deletions
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5
fs/btrfs/file.c
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@ -1411,7 +1411,7 @@ 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);
@ -1434,7 +1434,8 @@ 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);