Linux/linux 1f0ffa6drivers/md/bcache sysfs.c

bcache: only set BCACHE_DEV_WB_RUNNING when cached device attached

When people set a writeback percent via sysfs file,
  /sys/block/bcache<N>/bcache/writeback_percent
current code directly sets BCACHE_DEV_WB_RUNNING to dc->disk.flags
and schedules kworker dc->writeback_rate_update.

If there is no cache set attached to, the writeback kernel thread is
not running indeed, running dc->writeback_rate_update does not make
sense and may cause NULL pointer deference when reference cache set
pointer inside update_writeback_rate().

This patch checks whether the cache set point (dc->disk.c) is NULL in
sysfs interface handler, and only set BCACHE_DEV_WB_RUNNING and
schedule dc->writeback_rate_update when dc->disk.c is not NULL (it
means the cache device is attached to a cache set).

This problem might be introduced from initial bcache commit, but
commit 3fd47bfe55b0 ("bcache: stop dc->writeback_rate_update properly")
changes part of the original code piece, so I add 'Fixes: 3fd47bfe55b0'
to indicate from which commit this patch can be applied.

Fixes: 3fd47bfe55b0 ("bcache: stop dc->writeback_rate_update properly")
Reported-by: Bjørn Forsman <bjorn.forsman at gmail.com>
Signed-off-by: Coly Li <colyli at suse.de>
Reviewed-by: Bjørn Forsman <bjorn.forsman at gmail.com>
Cc: stable at vger.kernel.org
Signed-off-by: Jens Axboe <axboe at kernel.dk>
DeltaFile
+6-1drivers/md/bcache/sysfs.c
+6-11 files

UnifiedSplitRaw