[PATCH 0/11 v3] block: Fix block device shutdown related races

[Jan Kara <jack@suse.cz>]

Hello,

this is a series with the remaining patches (on top of 3.11-rc1) to fix several
different races and issues I've found when testing device shutdown and reuse.
The first two patches fix possible (theoretical) problems when opening of a
block device races with shutdown of a gendisk structure. Patches 3-9 fix oops
that is triggered by __blkdev_put() calling inode_detach_wb() too early (the
problem reported by Thiago). Patches 10 and 11 fix oops due to a bug in gendisk
code where get_gendisk() can return already freed gendisk structure (again
triggered by Omar's stress test).

People, please have a look at patches. They are mostly simple however the
interactions are rather complex so I may have missed something. Also I'm
happy for any additional testing these patches can get - I've stressed them
with Omar's script, tested memcg writeback, tested static (not udev managed)
device inodes.

Changes since v2:
* Added Tejun's acks
* Rebased on top of 4.11-rc1
* Fixed two possible races between blkdev_open() and del_gendisk()
* Fixed possible race between concurrent shutdown of cgwb spotted by Tejun

Changes since v1:
* Added Acks and Tested-by tags for patches in areas that did not change
* Reworked inode_detach_wb() related fixes based on Tejun's feedback

								Honza