From c933956ddf80bc455d33cbcf39d35d935daf45a9 Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Thu, 27 Feb 2014 13:58:04 +0800 Subject: [PATCH] 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: Miao Xie Signed-off-by: Josef Bacik --- 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 31e48b947060..fc2d21b0a022 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -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); -- 2.39.5