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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: Eric Wheeler <bcache@linux.ewheeler.net>
Tested-by: Marc MERLIN <marc@merlins.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
hifive-unleashed-5.1
Eric Wheeler 2016-02-26 14:39:06 -08:00 committed by Jens Axboe
parent 08095e7078
commit 07cc6ef8ed
1 changed files with 8 additions and 1 deletions
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9
drivers/md/bcache/super.c
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@ -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);