[Devel] [PATCH RHEL8 COMMIT] ploop: Sleepable push_backup_read

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-80.1.2.vz8.2.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-80.1.2.vz8.2.3
------>
commit 9c8c97ee9860292e3784e065661467bf578611ca
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Fri Oct 25 16:52:33 2019 +0300

    ploop: Sleepable push_backup_read
    
    Userspace calls this in separate thread and wants
    it is sleepable.
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 drivers/md/dm-ploop-cmd.c | 7 ++++---
 drivers/md/dm-ploop-map.c | 6 +++++-
 drivers/md/dm-ploop.h     | 1 +
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-ploop-cmd.c b/drivers/md/dm-ploop-cmd.c
index 0aa643d9c9fa..d329b5d62455 100644
--- a/drivers/md/dm-ploop-cmd.c
+++ b/drivers/md/dm-ploop-cmd.c
@@ -1291,6 +1291,7 @@ static struct push_backup *ploop_alloc_pb(struct ploop *ploop, char *uuid)
 	if (!pb)
 		return NULL;
 	snprintf(pb->uuid, sizeof(pb->uuid), "%s", uuid);
+	init_waitqueue_head(&pb->wq);
 	INIT_LIST_HEAD(&pb->pending);
 	pb->rb_root = RB_ROOT;
 
@@ -1444,13 +1445,13 @@ static int ploop_push_backup_read(struct ploop *ploop, char *uuid,
 		return -EINVAL;
 	if (!pb->alive)
 		return -ESTALE;
+	if (wait_event_interruptible(pb->wq, !list_empty_careful(&pb->pending)))
+		return -EINTR;
 
 	spin_lock_irq(&ploop->pb_lock);
 	h = orig_h = list_first_entry_or_null(&pb->pending, typeof(*h), list);
-	if (!h) {
-		result[0] = '\0';
+	if (WARN_ON_ONCE(!h))
 		goto unlock;
-	}
 	list_del_init(&h->list);
 
 	left = right = h->cluster;
diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 0fad19c69fa8..13cb5c9e2f04 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -963,8 +963,8 @@ static bool postpone_if_required_for_backup(struct ploop *ploop,
 			  struct bio *bio, unsigned int cluster)
 {
 	struct push_backup *pb = ploop->pb;
+	bool first, queue_timer = false;
 	struct dm_ploop_endio_hook *h;
-	bool queue_timer = false;
 
 	if (likely(!pb || !pb->alive))
 		return false;
@@ -992,9 +992,13 @@ static bool postpone_if_required_for_backup(struct ploop *ploop,
 
 	h = bio_to_endio_hook(bio);
 	link_endio_hook(ploop, h, &pb->rb_root, cluster, true);
+	first = list_empty(&pb->pending);
 	list_add_tail(&h->list, &pb->pending);
 	spin_unlock_irq(&ploop->pb_lock);
 
+	if (first)
+		wake_up_interruptible(&pb->wq);
+
 	if (queue_timer)
 		mod_timer(&pb->deadline_timer, BACKUP_DEADLINE * HZ + 1);
 
diff --git a/drivers/md/dm-ploop.h b/drivers/md/dm-ploop.h
index 1e1ab8ba476e..fc58e1081a78 100644
--- a/drivers/md/dm-ploop.h
+++ b/drivers/md/dm-ploop.h
@@ -147,6 +147,7 @@ struct push_backup {
 	/* This tree is for looking for delayed bio by cluster */
 	struct rb_root rb_root;
 
+	struct wait_queue_head wq;
 	struct list_head pending;
 };