tree 4b62c928d685a9badbdcb1a1048479ee9b8594f9
parent c06cb8b1c4d25e5b4d7a2d7c2462619de1e0dbc4
author Alasdair G Kergon <agk@redhat.com> 1163036682 -0800
committer Linus Torvalds <torvalds@g5.osdl.org> 1163039363 -0800

[PATCH] dm: fix find_device race

There is a race between dev_create() and find_device().

If the mdptr has not yet been stored against a device, find_device() needs to
behave as though no device was found.  It already returns NULL, but there is a
dm_put() missing: it must drop the reference dm_get_md() took.

The bug was introduced by dm-fix-mapped-device-ref-counting.patch.

It manifests itself if another dm ioctl attempts to reference a newly-created
device while the device creation ioctl is still running.  The consequence is
that the device cannot be removed until the machine is rebooted.  Certain udev
configurations can lead to this happening.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: <dm-devel@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>