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.

Fixes: b39f35ebe86d ("md: don't quiesce in mddev_suspend()")
Cc: stable@vger.kernel.org
Signed-off-by: Xiao Ni <xni@redhat.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20241106095124.74577-1-xni@redhat.com
Signed-off-by: Song Liu <song@kernel.org>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index f5ac81dd21b2bde260a85cb16fb5bc826bc97ea4..f09e7677ee9f1b4b61b469fc448caf20918afdbc 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -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;