linux-kernel - [PATCH 4.9 33/48] xfs: dont unconditionally clear the reflink flag on zero-block files

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Message-Id: <20171024125729.213459797@linuxfoundation.org>
Date:   Tue, 24 Oct 2017 15:03:46 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Amir Goldstein <amir73il@...il.com>,
        Carlos Maiolino <cmaiolino@...hat.com>,
        Christoph Hellwig <hch@....de>,
        "Darrick J. Wong" <darrick.wong@...cle.com>
Subject: [PATCH 4.9 33/48] xfs: dont unconditionally clear the reflink flag on zero-block files

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Darrick J. Wong <darrick.wong@...cle.com>

commit cc6f77710a6de6210f9feda7cd53e2f5ee7a7e69 upstream.

If we have speculative cow preallocations hanging around in the cow
fork, don't let a truncate operation clear the reflink flag because if
we do then there's a chance we'll forget to free those extents when we
destroy the incore inode.

Reported-by: Amir Goldstein <amir73il@...il.com>
Reviewed-by: Carlos Maiolino <cmaiolino@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/xfs/xfs_inode.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1632,10 +1632,12 @@ xfs_itruncate_extents(
 		goto out;

 	/*
-	 * Clear the reflink flag if we truncated everything.
+	 * Clear the reflink flag if there are no data fork blocks and
+	 * there are no extents staged in the cow fork.
 	 */
-	if (ip->i_d.di_nblocks == 0 && xfs_is_reflink_inode(ip)) {
-		ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
+	if (xfs_is_reflink_inode(ip) && ip->i_cnextents == 0) {
+		if (ip->i_d.di_nblocks == 0)
+			ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
 		xfs_inode_clear_cowblocks_tag(ip);
 	}