linux/drivers/md
Tejun Heo e525fd89d3 block: make blkdev_get/put() handle exclusive access
Over time, block layer has accumulated a set of APIs dealing with bdev
open, close, claim and release.

* blkdev_get/put() are the primary open and close functions.

* bd_claim/release() deal with exclusive open.

* open/close_bdev_exclusive() are combination of open and claim and
  the other way around, respectively.

* bd_link/unlink_disk_holder() to create and remove holder/slave
  symlinks.

* open_by_devnum() wraps bdget() + blkdev_get().

The interface is a bit confusing and the decoupling of open and claim
makes it impossible to properly guarantee exclusive access as
in-kernel open + claim sequence can disturb the existing exclusive
open even before the block layer knows the current open if for another
exclusive access.  Reorganize the interface such that,

* blkdev_get() is extended to include exclusive access management.
  @holder argument is added and, if is @FMODE_EXCL specified, it will
  gain exclusive access atomically w.r.t. other exclusive accesses.

* blkdev_put() is similarly extended.  It now takes @mode argument and
  if @FMODE_EXCL is set, it releases an exclusive access.  Also, when
  the last exclusive claim is released, the holder/slave symlinks are
  removed automatically.

* bd_claim/release() and close_bdev_exclusive() are no longer
  necessary and either made static or removed.

* bd_link_disk_holder() remains the same but bd_unlink_disk_holder()
  is no longer necessary and removed.

* open_bdev_exclusive() becomes a simple wrapper around lookup_bdev()
  and blkdev_get().  It also has an unexpected extra bdev_read_only()
  test which probably should be moved into blkdev_get().

* open_by_devnum() is modified to take @holder argument and pass it to
  blkdev_get().

Most of bdev open/close operations are unified into blkdev_get/put()
and most exclusive accesses are tested atomically at the open time (as
it should).  This cleans up code and removes some, both valid and
invalid, but unnecessary all the same, corner cases.

open_bdev_exclusive() and open_by_devnum() can use further cleanup -
rename to blkdev_get_by_path() and blkdev_get_by_devt() and drop
special features.  Well, let's leave them for another day.

Most conversions are straight-forward.  drbd conversion is a bit more
involved as there was some reordering, but the logic should stay the
same.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Brown <neilb@suse.de>
Acked-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Peter Osterlund <petero2@telia.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <joel.becker@oracle.com>
Cc: Alex Elder <aelder@sgi.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: dm-devel@redhat.com
Cc: drbd-dev@lists.linbit.com
Cc: Leo Chen <leochen@broadcom.com>
Cc: Scott Branden <sbranden@broadcom.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: Joern Engel <joern@logfs.org>
Cc: reiserfs-devel@vger.kernel.org
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
2010-11-13 11:55:17 +01:00
..
bitmap.c md: unplug writes to external bitmaps. 2010-10-29 16:40:32 +11:00
bitmap.h md: use sector_t in bitmap_get_counter 2010-10-28 17:32:26 +11:00
dm-bio-record.h
dm-crypt.c dm: implement REQ_FLUSH/FUA support for bio-based dm 2010-09-10 12:35:38 +02:00
dm-delay.c dm delay: support discard 2010-08-12 04:14:13 +01:00
dm-exception-store.c dm snapshot: test chunk size against both origin and snapshot 2010-08-12 04:13:51 +01:00
dm-exception-store.h dm snapshot: test chunk size against both origin and snapshot 2010-08-12 04:13:51 +01:00
dm-io.c dm: implement REQ_FLUSH/FUA support for bio-based dm 2010-09-10 12:35:38 +02:00
dm-ioctl.c llseek: automatically add .llseek fop 2010-10-15 15:53:27 +02:00
dm-kcopyd.c block: unify flags for struct bio and struct request 2010-08-07 18:20:39 +02:00
dm-linear.c dm: use dm_target_offset macro 2010-08-12 04:14:11 +01:00
dm-log-userspace-base.c
dm-log-userspace-transfer.c
dm-log-userspace-transfer.h
dm-log.c dm: implement REQ_FLUSH/FUA support for bio-based dm 2010-09-10 12:35:38 +02:00
dm-mpath.c dm mpath: support discard 2010-08-12 04:14:32 +01:00
dm-mpath.h
dm-path-selector.c
dm-path-selector.h
dm-queue-length.c
dm-raid1.c dm: implement REQ_FLUSH/FUA support for bio-based dm 2010-09-10 12:35:38 +02:00
dm-region-hash.c dm: implement REQ_FLUSH/FUA support for bio-based dm 2010-09-10 12:35:38 +02:00
dm-round-robin.c
dm-service-time.c
dm-snap-persistent.c workqueues: s/ON_STACK/ONSTACK/ 2010-10-26 16:52:14 -07:00
dm-snap-transient.c
dm-snap.c Merge branch 'for-2.6.37/barrier' of git://git.kernel.dk/linux-2.6-block 2010-10-22 17:07:18 -07:00
dm-stripe.c dm: implement REQ_FLUSH/FUA support for bio-based dm 2010-09-10 12:35:38 +02:00
dm-sysfs.c
dm-table.c block: make blkdev_get/put() handle exclusive access 2010-11-13 11:55:17 +01:00
dm-target.c dm: error return error for discards 2010-08-12 04:14:14 +01:00
dm-uevent.c
dm-uevent.h
dm-zero.c dm: zero silently drop discards 2010-08-12 04:14:12 +01:00
dm.c Merge branch 'for-2.6.37/barrier' of git://git.kernel.dk/linux-2.6-block 2010-10-22 17:07:18 -07:00
dm.h dm: linear support discard 2010-08-12 04:14:08 +01:00
faulty.c md: use separate bio pool for each md device. 2010-10-28 17:36:15 +11:00
Kconfig Merge branch 'async' of macbook:git/btrfs-unstable 2010-08-09 10:36:44 +01:00
linear.c md: implment REQ_FLUSH/FUA support 2010-09-10 12:35:38 +02:00
linear.h
Makefile Merge branch 'async' of macbook:git/btrfs-unstable 2010-08-09 10:36:44 +01:00
md.c block: make blkdev_get/put() handle exclusive access 2010-11-13 11:55:17 +01:00
md.h md: use separate bio pool for each md device. 2010-10-28 17:36:15 +11:00
multipath.c md: implment REQ_FLUSH/FUA support 2010-09-10 12:35:38 +02:00
multipath.h
raid0.c md: implment REQ_FLUSH/FUA support 2010-09-10 12:35:38 +02:00
raid0.h md: fix handling of array level takeover that re-arranges devices. 2010-06-24 13:33:24 +10:00
raid1.c md: tidy up device searches in read_balance. 2010-10-29 16:40:33 +11:00
raid1.h md/raid1: discard unused variable. 2010-10-29 16:40:33 +11:00
raid5.c md: use separate bio pool for each md device. 2010-10-28 17:36:15 +11:00
raid5.h md: implment REQ_FLUSH/FUA support 2010-09-10 12:35:38 +02:00
raid10.c md: use separate bio pool for each md device. 2010-10-28 17:36:15 +11:00
raid10.h md: fix handling of array level takeover that re-arranges devices. 2010-06-24 13:33:24 +10:00