[PATCH 15/15] xfs: poll waiting for quotacheck

["Darrick J. Wong" <darrick.wong@xxxxxxxxxx>]

From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>

Create a pwork destroy function that uses polling instead of
uninterruptible sleep to wait for work items to finish so that we can
touch the softlockup watchdog.  IOWs, gross hack.

Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
---
 fs/xfs/xfs_iwalk.c |    3 +++
 fs/xfs/xfs_iwalk.h |    3 ++-
 fs/xfs/xfs_pwork.c |   19 +++++++++++++++++++
 fs/xfs/xfs_pwork.h |    3 +++
 fs/xfs/xfs_qm.c    |    2 +-
 5 files changed, 28 insertions(+), 2 deletions(-)


diff --git a/fs/xfs/xfs_iwalk.c b/fs/xfs/xfs_iwalk.c
index f0277369e896..80c139aed264 100644
--- a/fs/xfs/xfs_iwalk.c
+++ b/fs/xfs/xfs_iwalk.c
@@ -588,6 +588,7 @@ xfs_iwalk_threaded(
 	xfs_ino_t		startino,
 	xfs_iwalk_fn		iwalk_fn,
 	unsigned int		inode_records,
+	bool			polled,
 	void			*data)
 {
 	struct xfs_pwork_ctl	pctl;
@@ -619,6 +620,8 @@ xfs_iwalk_threaded(
 		startino = XFS_AGINO_TO_INO(mp, agno + 1, 0);
 	}
 
+	if (polled)
+		xfs_pwork_poll(&pctl);
 	return xfs_pwork_destroy(&pctl);
 }
 
diff --git a/fs/xfs/xfs_iwalk.h b/fs/xfs/xfs_iwalk.h
index 22c31763a9b8..67462861680c 100644
--- a/fs/xfs/xfs_iwalk.h
+++ b/fs/xfs/xfs_iwalk.h
@@ -16,7 +16,8 @@ typedef int (*xfs_iwalk_fn)(struct xfs_mount *mp, struct xfs_trans *tp,
 int xfs_iwalk(struct xfs_mount *mp, struct xfs_trans *tp, xfs_ino_t startino,
 		xfs_iwalk_fn iwalk_fn, unsigned int inode_records, void *data);
 int xfs_iwalk_threaded(struct xfs_mount *mp, xfs_ino_t startino,
-		xfs_iwalk_fn iwalk_fn, unsigned int inode_records, void *data);
+		xfs_iwalk_fn iwalk_fn, unsigned int inode_records, bool poll,
+		void *data);
 
 /* Walk all inode btree records in the filesystem starting from @startino. */
 typedef int (*xfs_inobt_walk_fn)(struct xfs_mount *mp, struct xfs_trans *tp,
diff --git a/fs/xfs/xfs_pwork.c b/fs/xfs/xfs_pwork.c
index 779596ed9432..562ace9d5eb8 100644
--- a/fs/xfs/xfs_pwork.c
+++ b/fs/xfs/xfs_pwork.c
@@ -13,6 +13,7 @@
 #include "xfs_trace.h"
 #include "xfs_sysctl.h"
 #include "xfs_pwork.h"
+#include <linux/nmi.h>
 
 /*
  * Parallel Work Queue
@@ -46,6 +47,8 @@ xfs_pwork_work(
 	error = pctl->work_fn(pctl->mp, pwork);
 	if (error && !pctl->error)
 		pctl->error = error;
+	if (atomic_dec_and_test(&pctl->nr_work))
+		wake_up(&pctl->poll_wait);
 }
 
 /*
@@ -74,6 +77,8 @@ xfs_pwork_init(
 	pctl->work_fn = work_fn;
 	pctl->error = 0;
 	pctl->mp = mp;
+	atomic_set(&pctl->nr_work, 0);
+	init_waitqueue_head(&pctl->poll_wait);
 
 	return 0;
 }
@@ -86,6 +91,7 @@ xfs_pwork_queue(
 {
 	INIT_WORK(&pwork->work, xfs_pwork_work);
 	pwork->pctl = pctl;
+	atomic_inc(&pctl->nr_work);
 	queue_work(pctl->wq, &pwork->work);
 }
 
@@ -99,6 +105,19 @@ xfs_pwork_destroy(
 	return pctl->error;
 }
 
+/*
+ * Wait for the work to finish by polling completion status and touch the soft
+ * lockup watchdog.  This is for callers such as mount which hold locks.
+ */
+void
+xfs_pwork_poll(
+	struct xfs_pwork_ctl	*pctl)
+{
+	while (wait_event_timeout(pctl->poll_wait,
+				atomic_read(&pctl->nr_work) == 0, HZ) == 0)
+		touch_softlockup_watchdog();
+}
+
 /*
  * Return the amount of parallelism that the data device can handle, or 0 for
  * no limit.
diff --git a/fs/xfs/xfs_pwork.h b/fs/xfs/xfs_pwork.h
index 99a9d210d49e..8133124cf3bb 100644
--- a/fs/xfs/xfs_pwork.h
+++ b/fs/xfs/xfs_pwork.h
@@ -18,6 +18,8 @@ struct xfs_pwork_ctl {
 	struct workqueue_struct	*wq;
 	struct xfs_mount	*mp;
 	xfs_pwork_work_fn	work_fn;
+	struct wait_queue_head	poll_wait;
+	atomic_t		nr_work;
 	int			error;
 };
 
@@ -53,6 +55,7 @@ int xfs_pwork_init(struct xfs_mount *mp, struct xfs_pwork_ctl *pctl,
 		unsigned int nr_threads);
 void xfs_pwork_queue(struct xfs_pwork_ctl *pctl, struct xfs_pwork *pwork);
 int xfs_pwork_destroy(struct xfs_pwork_ctl *pctl);
+void xfs_pwork_poll(struct xfs_pwork_ctl *pctl);
 unsigned int xfs_pwork_guess_datadev_parallelism(struct xfs_mount *mp);
 
 #endif /* __XFS_PWORK_H__ */
diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index 8004c931c86e..8bb902125403 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -1304,7 +1304,7 @@ xfs_qm_quotacheck(
 		flags |= XFS_PQUOTA_CHKD;
 	}
 
-	error = xfs_iwalk_threaded(mp, 0, xfs_qm_dqusage_adjust, 0, NULL);
+	error = xfs_iwalk_threaded(mp, 0, xfs_qm_dqusage_adjust, 0, true, NULL);
 	if (error)
 		goto error_return;