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Commit c933956d authored by Miao Xie's avatar Miao Xie Committed by Josef Bacik
Browse files

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



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: default avatarMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
parent 9c9ca00b

fs/btrfs/file.c

+3 −2
Original line number Original line Diff line number Diff line
@@ -1411,7 +1411,7 @@ static noinline int check_can_nocow(struct inode *inode, loff_t pos, 
	int ret;

	int ret;





	lockstart = round_down(pos, root->sectorsize);

	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) {

	while (1) {

		lock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);

		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_DIRTY | EXTENT_DELALLOC |

				 EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG, 0, 0,

				 EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG, 0, 0,

				 NULL, GFP_NOFS);

				 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);

	unlock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);