From f1b92bbc2373902063d04d28bff1ab79edc00df3 Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Thu, 26 Oct 2017 09:31:16 -0700 Subject: [PATCH] xfs: drain the buffer LRU on mount Log recovery of v4 filesystems does not use buffer verifiers because log recovery historically can result in transient buffer corruption when target buffers might be ahead of the log after a crash. v5 filesystems work around this problem with metadata LSN ordering. While this log recovery verifier behavior is necessary on v4 supers, it can result in leaving buffers around in the LRU without verifiers attached for a significant amount of time. This leads to use of unverified buffers while the filesystem is in active use, long after recovery has completed. To address this problem, drain all buffers from the LRU as a final step of the log mount sequence. Note that this is done unconditionally to provide a consistently clean cache footprint, regardless of superblock version or log state. As a side effect, this ensures that all cache resident, unverified buffers are reclaimed after log recovery and therefore must be recreated with verifiers on subsequent use. Reported-by: Darrick Wong Signed-off-by: Brian Foster Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/xfs/xfs_log.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index dc95a49d62e7..ab59e78a5d87 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -744,6 +744,7 @@ xfs_log_mount_finish( { int error = 0; bool readonly = (mp->m_flags & XFS_MOUNT_RDONLY); + bool recovered = mp->m_log->l_flags & XLOG_RECOVERY_NEEDED; if (mp->m_flags & XFS_MOUNT_NORECOVERY) { ASSERT(mp->m_flags & XFS_MOUNT_RDONLY); @@ -780,6 +781,21 @@ xfs_log_mount_finish( mp->m_super->s_flags &= ~MS_ACTIVE; evict_inodes(mp->m_super); + /* + * Drain the buffer LRU after log recovery. This is required for v4 + * filesystems to avoid leaving around buffers with NULL verifier ops, + * but we do it unconditionally to make sure we're always in a clean + * cache state after mount. + * + * Don't push in the error case because the AIL may have pending intents + * that aren't removed until recovery is cancelled. + */ + if (!error && recovered) { + xfs_log_force(mp, XFS_LOG_SYNC); + xfs_ail_push_all_sync(mp->m_ail); + } + xfs_wait_buftarg(mp->m_ddev_targp); + if (readonly) mp->m_flags |= XFS_MOUNT_RDONLY;