[Devel] [PATCH RHEL8 COMMIT] ploop: Close race in ploop_flip_upper_deltas()

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-240.1.1.vz8.5.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-240.1.1.vz8.5.44
------>
commit 86f8bbf7fb0d5f4a0ef00e53a3ea137281ebbf35
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Thu Jun 17 19:03:22 2021 +0300

    ploop: Close race in ploop_flip_upper_deltas()
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    
    =====================
    Patchset description:
    
    ploop: Freeze WRITE on -ENOSPC on host
    
    Suspend WRITEs in case of host's fs returns -ENOSPC.
    
    https://jira.sw.ru/browse/PSBM-127225
    
    Kirill Tkhai (5):
          ploop: Add check of htable is empty on .dtr
          ploop: Rename delayed_pios into suspended_pios
          ploop: Remove unused define and comment
          ploop: Close race in ploop_flip_upper_deltas()
          ploop: Freeze on ENOSPC and notify userspace via dm event
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 drivers/md/dm-ploop-cmd.c    |  3 +--
 drivers/md/dm-ploop-target.c | 34 ++++++++++++++++++++++++++++++++++
 drivers/md/dm-ploop.h        |  2 ++
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-ploop-cmd.c b/drivers/md/dm-ploop-cmd.c
index 38b0ad40815e..2afe909171d8 100644
--- a/drivers/md/dm-ploop-cmd.c
+++ b/drivers/md/dm-ploop-cmd.c
@@ -1153,10 +1153,9 @@ static int ploop_set_noresume(struct ploop *ploop, char *mode)
 
 static int ploop_flip_upper_deltas(struct ploop *ploop)
 {
-	struct dm_target *ti = ploop->ti;
 	struct file *file;
 
-	if (!dm_suspended(ti) || !ploop->noresume || ploop->maintaince)
+	if (!ploop->suspended || !ploop->noresume || ploop->maintaince)
 		return -EBUSY;
 	if (ploop_is_ro(ploop))
 		return -EROFS;
diff --git a/drivers/md/dm-ploop-target.c b/drivers/md/dm-ploop-target.c
index 848e099d03a7..da241509af3b 100644
--- a/drivers/md/dm-ploop-target.c
+++ b/drivers/md/dm-ploop-target.c
@@ -411,6 +411,25 @@ static void ploop_status(struct dm_target *ti, status_type_t type,
 	read_unlock_irq(&ploop->bat_rwlock);
 }
 
+static void ploop_set_suspended(struct dm_target *ti, bool suspended)
+{
+	struct ploop *ploop = ti->private;
+
+	down_read(&ploop->ctl_rwsem);
+	ploop->suspended = suspended;
+	up_read(&ploop->ctl_rwsem);
+}
+
+static void ploop_presuspend(struct dm_target *ti)
+{
+}
+static void ploop_presuspend_undo(struct dm_target *ti)
+{
+}
+static void ploop_postsuspend(struct dm_target *ti)
+{
+	ploop_set_suspended(ti, true);
+}
 static int ploop_preresume(struct dm_target *ti)
 {
 	struct ploop *ploop = ti->private;
@@ -420,8 +439,19 @@ static int ploop_preresume(struct dm_target *ti)
 	if (ploop->noresume)
 		ret = -EAGAIN;
 	up_read(&ploop->ctl_rwsem);
+
+	if (ret == 0) {
+		/*
+		 * We are singleton target. There will be
+		 * no more reasons to break resume.
+		 */
+		ploop_set_suspended(ti, false);
+	}
 	return ret;
 }
+static void ploop_resume(struct dm_target *ti)
+{
+}
 
 /*----------------------------------------------------------------*/
 
@@ -434,7 +464,11 @@ static struct target_type ploop_target = {
 	.dtr = ploop_dtr,
 	.message = ploop_message,
 	.io_hints = ploop_io_hints,
+	.presuspend = ploop_presuspend,
+	.presuspend_undo = ploop_presuspend_undo,
+	.postsuspend = ploop_postsuspend,
 	.preresume = ploop_preresume,
+	.resume = ploop_resume,
 	.clone_and_map_rq = ploop_clone_and_map,
 	.status = ploop_status,
 };
diff --git a/drivers/md/dm-ploop.h b/drivers/md/dm-ploop.h
index d0f1493e12e6..143060d6cadf 100644
--- a/drivers/md/dm-ploop.h
+++ b/drivers/md/dm-ploop.h
@@ -185,6 +185,8 @@ struct ploop {
 
 	/* Resume is prohibited */
 	bool noresume;
+	/* Device is suspended */
+	bool suspended;
 
 	/* Maintaince in process */
 	bool maintaince;