Patch "md: drop queue limitation for RAID1 and RAID10" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    md: drop queue limitation for RAID1 and RAID10

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     md-drop-queue-limitation-for-raid1-and-raid10.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 0045dc91eaf802e52ec88b36cb0418325d92b126
Author: Mariusz Tkaczyk <mariusz.tkaczyk@xxxxxxxxxxxxxxx>
Date:   Fri Dec 17 10:29:55 2021 +0100

    md: drop queue limitation for RAID1 and RAID10
    
    [ Upstream commit a92ce0feffeed8b91f02dac85246d1205e4a64b6 ]
    
    As suggested by Neil Brown[1], this limitation seems to be
    deprecated.
    
    With plugging in use, writes are processed behind the raid thread
    and conf->pending_count is not increased. This limitation occurs only
    if caller doesn't use plugs.
    
    It can be avoided and often it is (with plugging). There are no reports
    that queue is growing to enormous size so remove queue limitation for
    non-plugged IOs too.
    
    [1] https://lore.kernel.org/linux-raid/162496301481.7211.18031090130574610495@xxxxxxxxxxxxxxxxxxxxx
    
    Signed-off-by: Mariusz Tkaczyk <mariusz.tkaczyk@xxxxxxxxxxxxxxx>
    Signed-off-by: Song Liu <song@xxxxxxxxxx>
    Stable-dep-of: 72c215ed8731 ("md/raid10: fix task hung in raid10d")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/md/raid1-10.c b/drivers/md/raid1-10.c
index 54db341639687..83f9a4f3d82e0 100644
--- a/drivers/md/raid1-10.c
+++ b/drivers/md/raid1-10.c
@@ -22,12 +22,6 @@
 
 #define BIO_SPECIAL(bio) ((unsigned long)bio <= 2)
 
-/* When there are this many requests queue to be written by
- * the raid thread, we become 'congested' to provide back-pressure
- * for writeback.
- */
-static int max_queued_requests = 1024;
-
 /* for managing resync I/O pages */
 struct resync_pages {
 	void		*raid_bio;
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 783763f6845f4..47997a9a3ca18 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1358,12 +1358,6 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 	r1_bio = alloc_r1bio(mddev, bio);
 	r1_bio->sectors = max_write_sectors;
 
-	if (conf->pending_count >= max_queued_requests) {
-		md_wakeup_thread(mddev->thread);
-		raid1_log(mddev, "wait queued");
-		wait_event(conf->wait_barrier,
-			   conf->pending_count < max_queued_requests);
-	}
 	/* first select target devices under rcu_lock and
 	 * inc refcount on their rdev.  Record them by setting
 	 * bios[x] to bio
@@ -3413,4 +3407,3 @@ MODULE_ALIAS("md-personality-3"); /* RAID1 */
 MODULE_ALIAS("md-raid1");
 MODULE_ALIAS("md-level-1");
 
-module_param(max_queued_requests, int, S_IRUGO|S_IWUSR);
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index c4c1a3a7d7abc..69708b455295b 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1387,12 +1387,6 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 		conf->reshape_safe = mddev->reshape_position;
 	}
 
-	if (conf->pending_count >= max_queued_requests) {
-		md_wakeup_thread(mddev->thread);
-		raid10_log(mddev, "wait queued");
-		wait_event(conf->wait_barrier,
-			   conf->pending_count < max_queued_requests);
-	}
 	/* first select target devices under rcu_lock and
 	 * inc refcount on their rdev.  Record them by setting
 	 * bios[x] to bio
@@ -5246,4 +5240,3 @@ MODULE_ALIAS("md-personality-9"); /* RAID10 */
 MODULE_ALIAS("md-raid10");
 MODULE_ALIAS("md-level-10");
 
-module_param(max_queued_requests, int, S_IRUGO|S_IWUSR);