[PATCH 2/3] Btrfs: fix wrong lock range and write size in check_can_nocow()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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

--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Filesystem Development]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux