From 696a562072e3c14bcd13ae5acc19cdf27679e865 Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Tue, 28 Mar 2017 14:51:44 -0700 Subject: xfs: use dedicated log worker wq to avoid deadlock with cil wq The log covering background task used to be part of the xfssyncd workqueue. That workqueue was removed as of commit 5889608df ("xfs: syncd workqueue is no more") and the associated work item scheduled to the xfs-log wq. The latter is used for log buffer I/O completion. Since xfs_log_worker() can invoke a log flush, a deadlock is possible between the xfs-log and xfs-cil workqueues. Consider the following codepath from xfs_log_worker(): xfs_log_worker() xfs_log_force() _xfs_log_force() xlog_cil_force() xlog_cil_force_lsn() xlog_cil_push_now() flush_work() The above is in xfs-log wq context and blocked waiting on the completion of an xfs-cil work item. Concurrently, the cil push in progress can end up blocked here: xlog_cil_push_work() xlog_cil_push() xlog_write() xlog_state_get_iclog_space() xlog_wait(&log->l_flush_wait, ...) The above is in xfs-cil context waiting on log buffer I/O completion, which executes in xfs-log wq context. In this scenario both workqueues are deadlocked waiting on eachother. Add a new workqueue specifically for the high level log covering and ail pushing worker, as was the case prior to commit 5889608df. Diagnosed-by: David Jeffery Signed-off-by: Brian Foster Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/xfs/xfs_mount.h | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/xfs/xfs_mount.h') diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h index 6db6fd6b82b0..22b2185e93a0 100644 --- a/fs/xfs/xfs_mount.h +++ b/fs/xfs/xfs_mount.h @@ -183,6 +183,7 @@ typedef struct xfs_mount { struct workqueue_struct *m_reclaim_workqueue; struct workqueue_struct *m_log_workqueue; struct workqueue_struct *m_eofblocks_workqueue; + struct workqueue_struct *m_sync_workqueue; /* * Generation of the filesysyem layout. This is incremented by each -- cgit v1.2.3-55-g7522