md: move bitmap_destroy to the beginning of __md_stop

Since we have switched to sync way to handle METADATA_UPDATED
msg for md-cluster, then process_metadata_update is depended
on mddev->thread->wqueue.

With the new change, clustered raid could possible hang if
array received a METADATA_UPDATED msg after array unregistered
mddev->thread, so we need to stop clustered raid (bitmap_destroy
-> bitmap_free -> md_cluster_stop) earlier than unregister
thread (mddev_detach -> md_unregister_thread).

And this change should be safe for non-clustered raid since
all writes are stopped before the destroy. Also in md_run,
we activate the personality (pers->run()) before activating
the bitmap (bitmap_create()). So it is pleasingly symmetric
to stop the bitmap (bitmap_destroy()) before stopping the
personality (__md_stop() calls pers->free()), we achieve this
by move bitmap_destroy to the beginning of __md_stop.

But we don't want to break the codes for waiting behind IO as
Shaohua mentioned, so introduce bitmap_wait_behind_writes to
call the codes, and call the new fun in both mddev_detach and
bitmap_destroy, then we will not break original behind IO code
and also fit the new condition well.

Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index b6fa55a..cc7bbd2 100644 (file)
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1764,6 +1764,20 @@ void bitmap_free(struct bitmap *bitmap)
 }
 EXPORT_SYMBOL(bitmap_free);
 
+void bitmap_wait_behind_writes(struct mddev *mddev)
+{
+       struct bitmap *bitmap = mddev->bitmap;
+
+       /* wait for behind writes to complete */
+       if (bitmap && atomic_read(&bitmap->behind_writes) > 0) {
+               pr_debug("md:%s: behind writes in progress - waiting to stop.\n",
+                        mdname(mddev));
+               /* need to kick something here to make sure I/O goes? */
+               wait_event(bitmap->behind_wait,
+                          atomic_read(&bitmap->behind_writes) == 0);
+       }
+}
+
 void bitmap_destroy(struct mddev *mddev)
 {
        struct bitmap *bitmap = mddev->bitmap;
@@ -1771,6 +1785,8 @@ void bitmap_destroy(struct mddev *mddev)
        if (!bitmap) /* there was no bitmap */
                return;
 
+       bitmap_wait_behind_writes(mddev);
+
        mutex_lock(&mddev->bitmap_info.mutex);
        spin_lock(&mddev->lock);
        mddev->bitmap = NULL; /* disconnect from the md device */

diff --git a/drivers/md/bitmap.h b/drivers/md/bitmap.h
index 9f76109..d15721a 100644 (file)
--- a/drivers/md/bitmap.h
+++ b/drivers/md/bitmap.h
@@ -271,6 +271,7 @@ struct bitmap *get_bitmap_from_slot(struct mddev *mddev, int slot);
 int bitmap_copy_from_slot(struct mddev *mddev, int slot,
                                sector_t *lo, sector_t *hi, bool clear_bits);
 void bitmap_free(struct bitmap *bitmap);
+void bitmap_wait_behind_writes(struct mddev *mddev);
 #endif
 
 #endif

diff --git a/drivers/md/md.c b/drivers/md/md.c
index af91187..42e68b2 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5675,15 +5675,7 @@ EXPORT_SYMBOL_GPL(md_stop_writes);
 
 static void mddev_detach(struct mddev *mddev)
 {
-       struct bitmap *bitmap = mddev->bitmap;
-       /* wait for behind writes to complete */
-       if (bitmap && atomic_read(&bitmap->behind_writes) > 0) {
-               pr_debug("md:%s: behind writes in progress - waiting to stop.\n",
-                        mdname(mddev));
-               /* need to kick something here to make sure I/O goes? */
-               wait_event(bitmap->behind_wait,
-                          atomic_read(&bitmap->behind_writes) == 0);
-       }
+       bitmap_wait_behind_writes(mddev);
        if (mddev->pers && mddev->pers->quiesce) {
                mddev->pers->quiesce(mddev, 1);
                mddev->pers->quiesce(mddev, 0);
@@ -5696,6 +5688,7 @@ static void mddev_detach(struct mddev *mddev)
 static void __md_stop(struct mddev *mddev)
 {
        struct md_personality *pers = mddev->pers;
+       bitmap_destroy(mddev);
        mddev_detach(mddev);
        /* Ensure ->event_work is done */
        flush_workqueue(md_misc_wq);
@@ -5716,7 +5709,6 @@ void md_stop(struct mddev *mddev)
         * This is called from dm-raid
         */
        __md_stop(mddev);
-       bitmap_destroy(mddev);
        if (mddev->bio_set)
                bioset_free(mddev->bio_set);
 }
@@ -5854,7 +5846,6 @@ static int do_md_stop(struct mddev *mddev, int mode,
        if (mode == 0) {
                pr_info("md: %s stopped.\n", mdname(mddev));
 
-               bitmap_destroy(mddev);
                if (mddev->bitmap_info.file) {
                        struct file *f = mddev->bitmap_info.file;
                        spin_lock(&mddev->lock);