lkml.org 
[lkml]   [2019]   [Jun]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.19 22/75] bcache: only set BCACHE_DEV_WB_RUNNING when cached device attached
Date
From: Coly Li <colyli@suse.de>

commit 1f0ffa67349c56ea54c03ccfd1e073c990e7411e upstream.

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@gmail.com>
Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Bjørn Forsman <bjorn.forsman@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/bcache/sysfs.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -393,8 +393,13 @@ STORE(bch_cached_dev)
if (attr == &sysfs_writeback_running)
bch_writeback_queue(dc);

+ /*
+ * Only set BCACHE_DEV_WB_RUNNING when cached device attached to
+ * a cache set, otherwise it doesn't make sense.
+ */
if (attr == &sysfs_writeback_percent)
- if (!test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags))
+ if ((dc->disk.c != NULL) &&
+ (!test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags)))
schedule_delayed_work(&dc->writeback_rate_update,
dc->writeback_rate_update_seconds * HZ);


\
 
 \ /
  Last update: 2019-06-17 23:25    [W:0.300 / U:0.308 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site