diff mbox

[4/6] xfs: relax is_reflink_inode assert in xfs_reflink_find_cow_mapping

Message ID 151295860143.30614.17097584029425726245.stgit@magnolia (mailing list archive)
State Accepted
Headers show

Commit Message

Darrick J. Wong Dec. 11, 2017, 2:16 a.m. UTC 
From: Darrick J. Wong <darrick.wong@oracle.com>

We don't hold the ilock through the entire sequence of xfs_writepage_map
-> xfs_map_cow -> xfs_reflink_find_cow_mapping.  This means that we can
race with another thread that is trying to clear the inode reflink flag,
with the result that the flag is set for the xfs_map_cow check but
cleared before we get to the assert in find_cow_mapping.  When this
happens, we blow the assert even though everything is fine.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/xfs_reflink.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)



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Comments

Christoph Hellwig Dec. 14, 2017, 4:38 p.m. UTC | #1 
On Sun, Dec 10, 2017 at 06:16:41PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> We don't hold the ilock through the entire sequence of xfs_writepage_map
> -> xfs_map_cow -> xfs_reflink_find_cow_mapping.  This means that we can
> race with another thread that is trying to clear the inode reflink flag,
> with the result that the flag is set for the xfs_map_cow check but
> cleared before we get to the assert in find_cow_mapping.  When this
> happens, we blow the assert even though everything is fine.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>
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diff mbox

Patch

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index e13f5ad..99c5852 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -490,8 +490,9 @@  xfs_reflink_find_cow_mapping(
 	struct xfs_iext_cursor		icur;
 
 	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL | XFS_ILOCK_SHARED));
-	ASSERT(xfs_is_reflink_inode(ip));
 
+	if (!xfs_is_reflink_inode(ip))
+		return false;
 	offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
 	if (!xfs_iext_lookup_extent(ip, ifp, offset_fsb, &icur, &got))
 		return false;