block: move cmdfilter from gendisk to request_queue

cmd_filter works only for the block layer SG_IO with SCSI block
devices. It breaks scsi/sg.c, bsg, and the block layer SG_IO with SCSI
character devices (such as st). We hit a kernel crash with them.

The problem is that cmd_filter code accesses to gendisk (having struct
blk_scsi_cmd_filter) via inode->i_bdev->bd_disk. It works for only
SCSI block device files. With character device files, inode->i_bdev
leads you to struct cdev. inode->i_bdev->bd_disk->blk_scsi_cmd_filter
isn't safe.

SCSI ULDs don't expose gendisk; they keep it private. bsg needs to be
independent on any protocols. We shouldn't change ULDs to expose their
gendisk.

This patch moves struct blk_scsi_cmd_filter from gendisk to
request_queue, a common object, which eveyone can access to.

The user interface doesn't change; users can change the filters via
/sys/block/. gendisk has a pointer to request_queue so the cmd_filter
code accesses to struct blk_scsi_cmd_filter.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 4889eb86a39e..2cba5ef97b2b 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -582,6 +582,8 @@ blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
 
         q->sg_reserved_size = INT_MAX;
 
+        blk_set_cmd_filter_defaults(&q->cmd_filter);
+
         /*
          * all done
          */