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 4.5-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-4.5 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-4.5/bcache-cleaned-up-error-handling-around-register_cache.patch
queue-4.5/bcache-fix-race-of-writeback-thread-starting-before-complete-initialization.patch
queue-4.5/bcache-fix-cache_set_flush-null-pointer-dereference-on-oom.patch
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