These changes were applied to scsi.git, branch "misc". This patch fixes a reference count bug in the SCSI tape driver which can be reproduced with the following:
* Boot with slub_debug=FZPU, tape drive attached * echo 1 > /sys/devices/... tape device pci path .../remove * Wait for device removal * echo 1 > /sys/kernel/slab/blkdev_queue/validate * Slub debug complains about corrupted poison pattern In commit 523e1d39 (block: make gendisk hold a reference to its queue) add_disk() and disk_release() were modified to get/put an additional reference on a disk queue to fix a reference counting discrepency between bdev release and SCSI device removal. The ST driver never calls add_disk(), so this commit introduced an extra kref put when the ST driver frees its struct gendisk. Attempts were made to fix this bug at the block level [1] but later abandoned due to floppy driver issues [2]. [1] https://lkml.org/lkml/2012/8/27/354 [2] https://lkml.org/lkml/2012/9/22/113 Regards, -- Joe >From f209bda3ee16a70e714b55c372ed4265bfa91784 Mon Sep 17 00:00:00 2001 From: Joe Lawrence <[email protected]> Date: Fri, 1 Mar 2013 17:32:30 -0500 Subject: [PATCH] st: Take additional queue ref in st_probe MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The SCSI tape driver employs a struct gendisk, calling alloc_disk() to create an instance, but does not register it via add_disk(). When the gendisk is torn down, disk_release() is called and expects to return a disk queue reference that add_disk() normally would have taken out. (See commit 523e1d39.) Fix the kref accounting by adding a blk_get_queue() to st_probe(). Signed-off-by: Joe Lawrence <[email protected]> Tested-by: Ewan Milne <[email protected]> Cc: Kai Mäkisara <[email protected]> Cc: James E.J. Bottomley <[email protected]> Cc: Ewan Milne <[email protected]> Cc: [email protected] --- drivers/scsi/st.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c index 98156a9..eef8ddc 100644 --- a/drivers/scsi/st.c +++ b/drivers/scsi/st.c @@ -4112,6 +4112,10 @@ static int st_probe(struct device *dev) tpnt->disk = disk; disk->private_data = &tpnt->driver; disk->queue = SDp->request_queue; + /* SCSI tape doesn't register this gendisk via add_disk(). Manually + * take queue reference that release_disk() expects. */ + if (!blk_get_queue(disk->queue)) + goto out_put_queue; tpnt->driver = &st_template; tpnt->device = SDp; @@ -4222,6 +4226,8 @@ out_put_index: spin_lock(&st_index_lock); idr_remove(&st_index_idr, dev_num); spin_unlock(&st_index_lock); +out_put_queue: + blk_put_queue(disk->queue); out_put_disk: put_disk(disk); kfree(tpnt); -- 1.8.1.2
