Messages in this thread | | | Date | Mon, 27 Apr 2015 10:27:55 -0600 | From | Jens Axboe <> | Subject | Re: [PATCH -stable] block: destroy bdi before blockdev is unregistered. |
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On 04/26/2015 10:12 PM, NeilBrown wrote: > > Because of the peculiar way that md devices are created (automatically > when the device node is opened), a new device can be created and > registered immediately after the > blk_unregister_region(disk_devt(disk), disk->minors); > call in del_gendisk(). > > Therefore it is important that all visible artifacts of the previous > device are removed before this call. In particular, the 'bdi'. > > Since: > commit c4db59d31e39ea067c32163ac961e9c80198fd37 > Author: Christoph Hellwig <hch@lst.de> > fs: don't reassign dirty inodes to default_backing_dev_info > > moved the > device_unregister(bdi->dev); > call from bdi_unregister() to bdi_destroy() it has been quite easy to > lose a race and have a new (e.g.) "md127" be created after the > blk_unregister_region() call and before bdi_destroy() is ultimately > called by the final 'put_disk', which must come after del_gendisk(). > > The new device finds that the bdi name is already registered in sysfs > and complains > >> [ 9627.630029] WARNING: CPU: 18 PID: 3330 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x5a/0x70() >> [ 9627.630032] sysfs: cannot create duplicate filename '/devices/virtual/bdi/9:127' > > We can fix this by moving the bdi_destroy() call out of > blk_release_queue() (which can happen very late when a refcount > reaches zero) and into blk_cleanup_queue() - which happens exactly when the md > device driver calls it. > > Then it is only necessary for md to call blk_cleanup_queue() before > del_gendisk(). As loop.c devices are also created on demand by > opening the device node, we make the same change there. > > Fixes: c4db59d31e39ea067c32163ac961e9c80198fd37 > Reported-by: Azat Khuzhin <a3at.mail@gmail.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: stable@vger.kernel.org (v4.0) > Signed-off-by: NeilBrown <neilb@suse.de> > > -- > Hi Jens, > if you could check this and forward on to Linus I'd really appreciate it.
Yup, I added it. BTW, that line needs 3 '-', otherwise git am will pick up the comments below :-)
Thanks Neil.
-- Jens Axboe
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