This is a note to let you know that I've just added the patch titled bcache: fix race of writeback thread starting before complete initialization to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bcache-fix-race-of-writeback-thread-starting-before-complete-initialization.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 07cc6ef8edc47f8b4fc1e276d31127a0a5863d4d Mon Sep 17 00:00:00 2001 From: Eric Wheeler <git@xxxxxxxxxxxxxxxxxx> Date: Fri, 26 Feb 2016 14:39:06 -0800 Subject: bcache: fix race of writeback thread starting before complete initialization From: Eric Wheeler <git@xxxxxxxxxxxxxxxxxx> commit 07cc6ef8edc47f8b4fc1e276d31127a0a5863d4d upstream. 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@xxxxxxxxxxxxxxxxxx> Tested-by: Marc MERLIN <marc@xxxxxxxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/md/bcache/super.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -1015,8 +1015,12 @@ int bch_cached_dev_attach(struct cached_ */ 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_ 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); Patches currently in stable-queue which might be from git@xxxxxxxxxxxxxxxxxx are queue-4.4/bcache-cleaned-up-error-handling-around-register_cache.patch queue-4.4/bcache-fix-race-of-writeback-thread-starting-before-complete-initialization.patch queue-4.4/bcache-fix-cache_set_flush-null-pointer-dereference-on-oom.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html