blkmq: Fix NULL pointer deref when all reserved tags in
authorSam Bradshaw <sbradshaw@micron.com>
Wed, 18 Mar 2015 23:06:18 +0000 (17:06 -0600)
committerJens Axboe <axboe@fb.com>
Wed, 18 Mar 2015 23:06:18 +0000 (17:06 -0600)
commitbc188d818edf325ae38cfa43254a0b10a4defd65
tree08dec19e40bccd2d87738686f94c15e31d121c67
parent9a30b096b543932de218dd3501b5562e00a8792d
blkmq: Fix NULL pointer deref when all reserved tags in

When allocating from the reserved tags pool, bt_get() is called with
a NULL hctx.  If all tags are in use, the hw queue is kicked to push
out any pending IO, potentially freeing tags, and tag allocation is
retried.  The problem is that blk_mq_run_hw_queue() doesn't check for
a NULL hctx.  So we avoid it with a simple NULL hctx test.

Tested by hammering mtip32xx with concurrent smartctl/hdparm.

Signed-off-by: Sam Bradshaw <sbradshaw@micron.com>
Signed-off-by: Selvan Mani <smani@micron.com>
Fixes: b32232073e80 ("blk-mq: fix hang in bt_get()")
Cc: stable@kernel.org
Added appropriate comment.

Signed-off-by: Jens Axboe <axboe@fb.com>
block/blk-mq-tag.c