rbd: avoid dropping extra reference in rbd_free_disk()
authorAlex Elder <elder@inktank.com>
Fri, 26 Apr 2013 04:15:08 +0000 (23:15 -0500)
committerSage Weil <sage@inktank.com>
Thu, 2 May 2013 04:19:32 +0000 (21:19 -0700)
commita0cab924324fac8d6414009bc25ce31eeece038e
treed8b180f239a010df65a11d80047be25b33626052
parentf40eb349e032bee2b6f06e9b6f1dbfae561bd30a
rbd: avoid dropping extra reference in rbd_free_disk()

I found during some failure injection testing that the call to
rbd_free_disk() in the error path of rbd_dev_probe_finish() was
dropping an extra reference to the disk queue.  The problem
occurred when put_disk tried to drop a reference to the disk's
queue.  A call to blk_cleanup_queue() just prior to that will have
also dropped a reference to the queue.

The problem is that the reference dropped by put_disk() is assumed
to have been taken by add_disk().  Our code has error paths that can
occur after the disk and its queue are initialized, but before the
call to add_disk(), and in those paths we won't have that extra
reference.

The fix is easy though.  In rbd_free_disk() we're already checking
the disk's GENHD_FL_UP flag.  That flag is an indication that
add_disk() has been called, so just call blk_cleanup_queue()
conditional on that flag being set.

This resolves:
    http://tracker.ceph.com/issues/4800

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
drivers/block/rbd.c