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md: move bitmap_destroy to the beginning of __md_stop

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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>
This commit is contained in:
Guoqing Jiang 2017-03-14 09:40:20 +08:00 committed by Shaohua Li
parent ea17481fb4
commit 48df498daf
3 changed files with 19 additions and 11 deletions
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16
drivers/md/bitmap.c
View File

@ -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 */

1
drivers/md/bitmap.h
View File

@ -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

13
drivers/md/md.c
View File

@ -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);