[PATCH V2 1/1] Add mddev->io_acct_cnt for raid0_quiesce

[Xiao Ni <xni@redhat.com>]

It has added io_acct_set for raid0/raid5 io accounting and it needs to
alloc md_io_acct in the i/o path. They are free when the bios come back
from member disks. Now we don't have a method to monitor if those bios
are all come back. In the takeover process, it needs to free the raid0
memory resource including the memory pool for md_io_acct. But maybe some
bios are still not returned. When those bios are returned, it can cause
panic bcause of introducing NULL pointer or invalid address.

This patch adds io_acct_cnt. So when stopping raid0, it can use this
to wait until all bios come back.

Reported-by: Fine Fan <ffan@redhat.com>
Signed-off-by: Xiao Ni <xni@redhat.com>
---
V2: Move struct mddev* to the start of struct mddev_io_acct
 drivers/md/md.c    | 13 ++++++++++++-
 drivers/md/md.h    | 11 ++++++++---
 drivers/md/raid0.c |  6 ++++++
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 6f3b2c1cb6cd..208f69849054 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -685,6 +685,7 @@ void mddev_init(struct mddev *mddev)
 	atomic_set(&mddev->flush_pending, 0);
 	init_waitqueue_head(&mddev->sb_wait);
 	init_waitqueue_head(&mddev->recovery_wait);
+	init_waitqueue_head(&mddev->wait_io_acct);
 	mddev->reshape_position = MaxSector;
 	mddev->reshape_backwards = 0;
 	mddev->last_sync_action = "none";
@@ -8618,15 +8619,18 @@ int acct_bioset_init(struct mddev *mddev)
 {
 	int err = 0;
 
-	if (!bioset_initialized(&mddev->io_acct_set))
+	if (!bioset_initialized(&mddev->io_acct_set)) {
+		atomic_set(&mddev->io_acct_cnt, 0);
 		err = bioset_init(&mddev->io_acct_set, BIO_POOL_SIZE,
 			offsetof(struct md_io_acct, bio_clone), 0);
+	}
 	return err;
 }
 EXPORT_SYMBOL_GPL(acct_bioset_init);
 
 void acct_bioset_exit(struct mddev *mddev)
 {
+	WARN_ON(atomic_read(&mddev->io_acct_cnt) != 0);
 	bioset_exit(&mddev->io_acct_set);
 }
 EXPORT_SYMBOL_GPL(acct_bioset_exit);
@@ -8635,12 +8639,17 @@ static void md_end_io_acct(struct bio *bio)
 {
 	struct md_io_acct *md_io_acct = bio->bi_private;
 	struct bio *orig_bio = md_io_acct->orig_bio;
+	struct mddev *mddev = md_io_acct->mddev;
 
 	orig_bio->bi_status = bio->bi_status;
 
 	bio_end_io_acct(orig_bio, md_io_acct->start_time);
 	bio_put(bio);
 	bio_endio(orig_bio);
+
+	if (atomic_dec_and_test(&mddev->io_acct_cnt))
+		if (unlikely(test_bit(MD_QUIESCE, &mddev->flags)))
+			wake_up(&mddev->wait_io_acct);
 }
 
 /*
@@ -8660,6 +8669,8 @@ void md_account_bio(struct mddev *mddev, struct bio **bio)
 	md_io_acct = container_of(clone, struct md_io_acct, bio_clone);
 	md_io_acct->orig_bio = *bio;
 	md_io_acct->start_time = bio_start_io_acct(*bio);
+	md_io_acct->mddev = mddev;
+	atomic_inc(&mddev->io_acct_cnt);
 
 	clone->bi_end_io = md_end_io_acct;
 	clone->bi_private = md_io_acct;
diff --git a/drivers/md/md.h b/drivers/md/md.h
index b4e2d8b87b61..a7c89ed53be5 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -255,6 +255,7 @@ struct md_cluster_info;
  *		   array is ready yet.
  * @MD_BROKEN: This is used to stop writes and mark array as failed.
  * @MD_DELETED: This device is being deleted
+ * @MD_QUIESCE: This device is being quiesced. Now only raid0 use this flag
  *
  * change UNSUPPORTED_MDDEV_FLAGS for each array type if new flag is added
  */
@@ -272,6 +273,7 @@ enum mddev_flags {
 	MD_NOT_READY,
 	MD_BROKEN,
 	MD_DELETED,
+	MD_QUIESCE,
 };
 
 enum mddev_sb_flags {
@@ -513,6 +515,8 @@ struct mddev {
 						   * metadata and bitmap writes
 						   */
 	struct bio_set			io_acct_set; /* for raid0 and raid5 io accounting */
+	atomic_t			io_acct_cnt;
+	wait_queue_head_t		wait_io_acct;
 
 	/* Generic flush handling.
 	 * The last to finish preflush schedules a worker to submit
@@ -710,9 +714,10 @@ struct md_thread {
 };
 
 struct md_io_acct {
-	struct bio *orig_bio;
-	unsigned long start_time;
-	struct bio bio_clone;
+	struct mddev	*mddev;
+	struct bio	*orig_bio;
+	unsigned long	start_time;
+	struct bio	bio_clone;
 };
 
 #define THREAD_WAKEUP  0
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 857c49399c28..aced0ad8cdab 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -754,6 +754,12 @@ static void *raid0_takeover(struct mddev *mddev)
 
 static void raid0_quiesce(struct mddev *mddev, int quiesce)
 {
+	/* It doesn't use a separate struct to count how many bios are submitted
+	 * to member disks to avoid memory alloc and performance decrease
+	 */
+	set_bit(MD_QUIESCE, &mddev->flags);
+	wait_event(mddev->wait_io_acct, !atomic_read(&mddev->io_acct_cnt));
+	clear_bit(MD_QUIESCE, &mddev->flags);
 }
 
 static struct md_personality raid0_personality=
-- 
2.32.0 (Apple Git-132)