From fa5a4f57ddbece604e07abfe98e01f520635411d Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Tue, 21 Jun 2016 11:53:28 +1000 Subject: [PATCH] xfs: cancel eofblocks background trimming on remount read-only The filesystem quiesce sequence performs the operations necessary to drain all background work, push pending transactions through the log infrastructure and wait on I/O resulting from the final AIL push. We have had reports of remount,ro hangs in xfs_log_quiesce() -> xfs_wait_buftarg(), however, and some instrumentation code to detect transaction commits at this point in the quiesce sequence has inculpated the eofblocks background scanner as a cause. While higher level remount code generally prevents user modifications by the time the filesystem has made it to xfs_log_quiesce(), the background scanner may still be alive and can perform pending work at any time. If this occurs between the xfs_log_force() and xfs_wait_buftarg() calls within xfs_log_quiesce(), this can lead to an indefinite lockup in xfs_wait_buftarg(). To prevent this problem, cancel the background eofblocks scan worker during the remount read-only quiesce sequence. This suspends background trimming when a filesystem is remounted read-only. This is only done in the remount path because the freeze codepath has already locked out new transactions by the time the filesystem attempts to quiesce (and thus waiting on an active work item could deadlock). Kick the eofblocks worker to pick up where it left off once an fs is remounted back to read-write. Signed-off-by: Brian Foster Reviewed-by: Eric Sandeen Signed-off-by: Dave Chinner --- fs/xfs/xfs_icache.c | 2 +- fs/xfs/xfs_icache.h | 1 + fs/xfs/xfs_super.c | 8 ++++++++ 3 files changed, 10 insertions(+), 1 deletion(-) diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c index 99ee6eee5e0b..fb39a66914dd 100644 --- a/fs/xfs/xfs_icache.c +++ b/fs/xfs/xfs_icache.c @@ -765,7 +765,7 @@ restart: * Background scanning to trim post-EOF preallocated space. This is queued * based on the 'speculative_prealloc_lifetime' tunable (5m by default). */ -STATIC void +void xfs_queue_eofblocks( struct xfs_mount *mp) { diff --git a/fs/xfs/xfs_icache.h b/fs/xfs/xfs_icache.h index 62f1f91c32cb..05bac99bef75 100644 --- a/fs/xfs/xfs_icache.h +++ b/fs/xfs/xfs_icache.h @@ -68,6 +68,7 @@ void xfs_inode_clear_eofblocks_tag(struct xfs_inode *ip); int xfs_icache_free_eofblocks(struct xfs_mount *, struct xfs_eofblocks *); int xfs_inode_free_quota_eofblocks(struct xfs_inode *ip); void xfs_eofblocks_worker(struct work_struct *); +void xfs_queue_eofblocks(struct xfs_mount *); int xfs_inode_ag_iterator(struct xfs_mount *mp, int (*execute)(struct xfs_inode *ip, int flags, void *args), diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c index 11ea5d51db56..2d2810851871 100644 --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -1294,6 +1294,7 @@ xfs_fs_remount( */ xfs_restore_resvblks(mp); xfs_log_work_queue(mp); + xfs_queue_eofblocks(mp); } /* rw -> ro */ @@ -1306,6 +1307,13 @@ xfs_fs_remount( * return it to the same size. */ xfs_save_resvblks(mp); + + /* + * Cancel background eofb scanning so it cannot race with the + * final log force+buftarg wait and deadlock the remount. + */ + cancel_delayed_work_sync(&mp->m_eofblocks_work); + xfs_quiesce_attr(mp); mp->m_flags |= XFS_MOUNT_RDONLY; } -- 2.39.5