Messages in this thread | | | Date | Tue, 18 Oct 2011 15:08:01 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] block: make gendisk hold a reference to its queue |
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On 2011-10-18 04:55, Tejun Heo wrote: > On Mon, Oct 17, 2011 at 01:44:09PM +0200, Jens Axboe wrote: >> On 2011-10-17 04:43, Tejun Heo wrote: >>> The following command sequence triggers an oops. >>> >>> # mount /dev/sdb1 /mnt >>> # echo 1 > /sys/class/scsi_device/0\:0\:1\:0/device/delete >>> # umount /mnt >>> >>> general protection fault: 0000 [#1] PREEMPT SMP >>> CPU 2 >>> Modules linked in: >>> >>> Pid: 791, comm: umount Not tainted 3.1.0-rc3-work+ #8 Bochs Bochs >>> RIP: 0010:[<ffffffff810d0879>] [<ffffffff810d0879>] __lock_acquire+0x389/0x1d60 >>> ... >>> Call Trace: >>> [<ffffffff810d2845>] lock_acquire+0x95/0x140 >>> [<ffffffff81aed87b>] _raw_spin_lock+0x3b/0x50 >>> [<ffffffff811573bc>] bdi_lock_two+0x5c/0x70 >>> [<ffffffff811c2f6c>] bdev_inode_switch_bdi+0x4c/0xf0 >>> [<ffffffff811c3fcb>] __blkdev_put+0x11b/0x1d0 >>> [<ffffffff811c4010>] __blkdev_put+0x160/0x1d0 >>> [<ffffffff811c40df>] blkdev_put+0x5f/0x190 >>> [<ffffffff8118f18d>] kill_block_super+0x4d/0x80 >>> [<ffffffff8118f4a5>] deactivate_locked_super+0x45/0x70 >>> [<ffffffff8119003a>] deactivate_super+0x4a/0x70 >>> [<ffffffff811ac4ad>] mntput_no_expire+0xed/0x130 >>> [<ffffffff811acf2e>] sys_umount+0x7e/0x3a0 >>> [<ffffffff81aeeeab>] system_call_fastpath+0x16/0x1b >>> >>> This is because bdev holds on to disk but disk doesn't pin the >>> associated queue. If a SCSI device is removed while the device is >>> still open, the sdev puts the base reference to the queue on release. >>> When the bdev is finally released, the associated queue is already >>> gone along with the bdi and bdev_inode_switch_bdi() ends up >>> dereferencing already freed bdi. >>> >>> Even if it were not for this bug, disk not holding onto the associated >>> queue is very unusual and error-prone. >>> >>> Fix it by making add_disk() take an extra reference to its queue and >>> put it on disk_release() and ensuring that disk and its fops owner are >>> put in that order after all accesses to the disk and queue are >>> complete. >> >> Thanks, applied. > > Ooh, I had the WARN_ON_ONCE() condition wrong in add_disk() as > blk_get_queue() returns 1 on failure and 0 on success. Can you please > flip that?
Oops, I'll fix that one up.
-- Jens Axboe
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