FAILED: patch "[PATCH] md/raid5: Wait sync io to finish before changing group cnt" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x fa1944bbe6220eb929e2c02e5e8706b908565711
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024120641-carat-unwired-140a@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From fa1944bbe6220eb929e2c02e5e8706b908565711 Mon Sep 17 00:00:00 2001
From: Xiao Ni <[email protected]>
Date: Wed, 6 Nov 2024 17:51:24 +0800
Subject: [PATCH] md/raid5: Wait sync io to finish before changing group cnt

One customer reports a bug: raid5 is hung when changing thread cnt while resync is running. The stripes are all in conf->handle_list and new threads can't handle them.

Commit b39f35ebe86d ("md: don't quiesce in mddev_suspend()") removes pers->quiesce from mddev_suspend/resume. Before this patch, mddev_suspend needs to wait for all ios including sync io to finish. Now it's used to only wait normal io.

Fix this by calling raid5_quiesce from raid5_store_group_thread_cnt directly to wait all sync requests to finish before changing the group cnt.

index f5ac81dd21b2..f09e7677ee9f 100644
@@ -7176,6 +7176,8 @@ raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
 	err = mddev_suspend_and_lock(mddev);
 	if (err)
 		return err;
+	raid5_quiesce(mddev, true);
+
 	conf = mddev->private;
 	if (!conf)
 		err = -ENODEV;

@@ -7197,6 +7199,8 @@ raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
 			kfree(old_groups);
 		}
 	}
+
+	raid5_quiesce(mddev, false);
 	mddev_unlock_and_resume(mddev);
 
 	return err ?: len;