[PATCH v4 0/29] block: Make blkdev_get_by_*() return handle

[Jan Kara]

Hello,

this is a v3 of the patch series which implements the idea of blkdev_get_by_*()
calls returning bdev_handle which is then passed to blkdev_put() [1]. This
makes the get and put calls for bdevs more obviously matching and allows us to
propagate context from get to put without having to modify all the users
(again!). In particular I need to propagate used open flags to blkdev_put() to
be able count writeable opens and add support for blocking writes to mounted
block devices. I'll send that series separately.

The series is based on Btrfs tree's for-next branch [2] as of today as the
series depends on Christoph's changes to btrfs device handling.  Patches have
passed some reasonable testing - I've tested block changes, md, dm, bcache,
xfs, btrfs, ext4, swap. More testing or review is always welcome. Thanks! I've
pushed out the full branch to:

git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git bdev_handle

to ease review / testing. Christian, can you pull the patches to your tree
to get some exposure in linux-next as well? Thanks!

Changes since v3:
* Rebased on top on btrfs tree

Changes since v2:
* Rebased on top of current vfs tree
* Added some acks
* Reflected minor nits from Christoph
* Added missing conversion of blkdev_put() calls in cramfs and erofs
* Fixed possible leak of bdev handle in xfs if logdev is the same as fs dev

Changes since v1:
* Rebased on top of current vfs tree
* Renamed final functions to bdev_open_by_*() and bdev_release()
* Fixed detection of exclusive open in blkdev_ioctl() and blkdev_fallocate()
* Fixed swap conversion to properly reinitialize swap_info->bdev_handle
* Fixed xfs conversion to not oops with rtdev without logdev
* Couple other minor fixups

								Honza

[1] https://lore.kernel.org/all/ZJGNsVDhZx0Xgs2H@infradead.org
[2] git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next

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Previous versions:
Link: http://lore.kernel.org/r/20230629165206.383-1-jack@suse.cz # v1
Link: http://lore.kernel.org/r/20230810171429.31759-1-jack@suse.cz # v2