Commit 2f73d3c5 authored Sep 10, 2014 by NeilBrown

md/raid1: make sure resync waits for conflicting writes to complete.



The resync/recovery process for raid1 was recently changed
so that writes could happen in parallel with resync providing
they were in different regions of the device.

There is a problem though:  While a write request will always
wait for conflicting resync to complete, a resync request
will *not* always wait for conflicting writes to complete.

Two changes are needed to fix this:

1/ raise_barrier (which waits until it is safe to do resync)
   must wait until current_window_requests is zero
2/ wait_battier (which waits at the start of a new write request)
   must update current_window_requests if the request could
   possible conflict with a concurrent resync.

As concurrent writes and resync can lead to data loss,
this patch is suitable for -stable.

Fixes: 79ef3a8a
Cc: stable@vger.kernel.org (v3.13+)
Cc: majianpeng <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

parent 669cc7ba

drivers/md/raid1.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -845,10 +845,12 @@ static void raise_barrier(struct r1conf *conf)
		* C: next_resync + RESYNC_SECTORS > start_next_window, meaning
		* next resync will reach to the window which normal bios are
		* handling.
		* D: while there are any active requests in the current window.
		*/
		wait_event_lock_irq(conf->wait_barrier,
		!conf->array_frozen &&
		conf->barrier < RESYNC_DEPTH &&
		conf->current_window_requests == 0 &&
		(conf->start_next_window >=
		conf->next_resync + RESYNC_SECTORS),
		conf->resync_lock);
		@@ -915,8 +917,8 @@ static sector_t wait_barrier(struct r1conf conf, struct bio bio)
		}

		if (bio && bio_data_dir(bio) == WRITE) {
		if (conf->next_resync + NEXT_NORMALIO_DISTANCE
		<= bio->bi_iter.bi_sector) {
		if (bio->bi_iter.bi_sector >=
		conf->next_resync) {
		if (conf->start_next_window == MaxSector)
		conf->start_next_window =
		conf->next_resync +

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