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Commit 07cc6ef8 authored by Eric Wheeler's avatar Eric Wheeler Committed by Jens Axboe
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bcache: fix race of writeback thread starting before complete initialization 

The bch_writeback_thread might BUG_ON in read_dirty() if
dc->sb==BDEV_STATE_DIRTY and bch_sectors_dirty_init has not yet completed
its related initialization.  This patch downs the dc->writeback_lock until
after initialization is complete, thus preventing bch_writeback_thread
from proceeding prematurely.

See this thread:
  http://thread.gmane.org/gmane.linux.kernel.bcache.devel/3453



Signed-off-by: default avatarEric Wheeler <bcache@linux.ewheeler.net>
Tested-by: default avatarMarc MERLIN <marc@merlins.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 08095e70

drivers/md/bcache/super.c

+8 −1
Original line number Diff line number Diff line
@@ -1015,8 +1015,12 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c) 
	 */

	atomic_set(&dc->count, 1);



	if (bch_cached_dev_writeback_start(dc))

	/* Block writeback thread, but spawn it */

	down_write(&dc->writeback_lock);

	if (bch_cached_dev_writeback_start(dc)) {

		up_write(&dc->writeback_lock);

		return -ENOMEM;

	}



	if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {

		bch_sectors_dirty_init(dc);
@@ -1028,6 +1032,9 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c) 
	bch_cached_dev_run(dc);

	bcache_device_link(&dc->disk, c, "bdev");



	/* Allow the writeback thread to proceed */

	up_write(&dc->writeback_lock);



	pr_info("Caching %s as %s on set %pU",

		bdevname(dc->bdev, buf), dc->disk.disk->disk_name,

		dc->disk.c->sb.set_uuid);