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authorOmar Sandoval <osandov@fb.com>2017-09-17 14:06:58 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-09-20 08:20:01 +0200
commit81286ade81f73e895fe2edf89f3e8054a595ebe5 (patch)
tree2d7ad13ee2513f073a581b3a2480bb5535a3e247
parent63d184d2955bab0584acc10b502e415ce23394b1 (diff)
downloadlinux-linaro-stable-81286ade81f73e895fe2edf89f3e8054a595ebe5.tar.gz
xfs: check for race with xfs_reclaim_inode() in xfs_ifree_cluster()
commit f2e9ad212def50bcf4c098c6288779dd97fff0f0 upstream. After xfs_ifree_cluster() finds an inode in the radix tree and verifies that the inode number is what it expected, xfs_reclaim_inode() can swoop in and free it. xfs_ifree_cluster() will then happily continue working on the freed inode. Most importantly, it will mark the inode stale, which will probably be overwritten when the inode slab object is reallocated, but if it has already been reallocated then we can end up with an inode spuriously marked stale. In 8a17d7ddedb4 ("xfs: mark reclaimed inodes invalid earlier") we added a second check to xfs_iflush_cluster() to detect this race, but the similar RCU lookup in xfs_ifree_cluster() needs the same treatment. Signed-off-by: Omar Sandoval <osandov@fb.com> Reviewed-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/xfs/xfs_icache.c10
-rw-r--r--fs/xfs/xfs_inode.c23
2 files changed, 23 insertions, 10 deletions
diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index e279882de427..86a4911520cc 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -1078,11 +1078,11 @@ reclaim:
* Because we use RCU freeing we need to ensure the inode always appears
* to be reclaimed with an invalid inode number when in the free state.
* We do this as early as possible under the ILOCK so that
- * xfs_iflush_cluster() can be guaranteed to detect races with us here.
- * By doing this, we guarantee that once xfs_iflush_cluster has locked
- * XFS_ILOCK that it will see either a valid, flushable inode that will
- * serialise correctly, or it will see a clean (and invalid) inode that
- * it can skip.
+ * xfs_iflush_cluster() and xfs_ifree_cluster() can be guaranteed to
+ * detect races with us here. By doing this, we guarantee that once
+ * xfs_iflush_cluster() or xfs_ifree_cluster() has locked XFS_ILOCK that
+ * it will see either a valid inode that will serialise correctly, or it
+ * will see an invalid inode that it can skip.
*/
spin_lock(&ip->i_flags_lock);
ip->i_flags = XFS_IRECLAIM;
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 98cd905eadca..9e795ab08a53 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -2368,11 +2368,24 @@ retry:
* already marked stale. If we can't lock it, back off
* and retry.
*/
- if (ip != free_ip &&
- !xfs_ilock_nowait(ip, XFS_ILOCK_EXCL)) {
- rcu_read_unlock();
- delay(1);
- goto retry;
+ if (ip != free_ip) {
+ if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL)) {
+ rcu_read_unlock();
+ delay(1);
+ goto retry;
+ }
+
+ /*
+ * Check the inode number again in case we're
+ * racing with freeing in xfs_reclaim_inode().
+ * See the comments in that function for more
+ * information as to why the initial check is
+ * not sufficient.
+ */
+ if (ip->i_ino != inum + i) {
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ continue;
+ }
}
rcu_read_unlock();