[PATCH 0/7] block: reread partitions improvements

Jarod Wilson
2015-04-08T06:23:39Z

For loop, the root cause is one ABBA and one AA lock dependency
issue, and the two are fixed by patch 2 and patch 3 each.

Another reason is from the trylock in blkdev_reread_part(), which
may cause partition scanning failure too sometimes when another task
is holding the bd_mutex. In the discussion[1], both Tejun and Christoph
suggests to replace the trylock with mutex_lock in blkdev_reread_part(),
also Christoph suggests to export blkdev_reread_part.

Following the discussion, this patchset exports blkdev_reread_part(), and
introduces lockless __blkdev_reread_part() for fixing loop's AA lock issue.
Then ioctl_by_bdev(BLKRRPART) in loop, nbd and dasd is replaced with
blkdev_reread_part(). In the last patch, trylock in blkdev_reread_part()
is replaced with mutex_lock, and some analysis is provided about the
conversion.

This is a slightly reworked set from what Ming sent a few days ago,
based on Christoph's feedback. I've tested this out quite succesfully
in the scenario that prompted my first patch as well.

[1], https://lkml.org/lkml/2015/1/26/137
[2], https://lkml.org/lkml/2015/3/31/888

Jarod Wilson (3):
block: export blkdev_reread_part() and __blkdev_reread_part()
block: loop: fix another reread part failure
s390/block/dasd: remove obsolete while -EBUSY loop

Ming Lei (4):
block: loop: don't hold lo_ctl_mutex in lo_open
block: nbd: convert to blkdev_reread_part()
block: dasd_genhd: convert to blkdev_reread_part
block: replace trylock with mutex_lock in blkdev_reread_part()

block/ioctl.c | 34 +++++++++++++++++++----
drivers/block/loop.c | 60 ++++++++++++++++++++++++++++++++++-------
drivers/block/loop.h | 1 +
drivers/block/nbd.c | 2 +-
drivers/s390/block/dasd_genhd.c | 22 +++++----------
include/linux/fs.h | 3 +++
6 files changed, 90 insertions(+), 32 deletions(-)

CC: Christoph Hellwig <hch@infradead.org>
CC: Jens Axboe <axboe@kernel.dk>
CC: Tejun Heo <tj@kernel.org>
CC: Alexander Viro <viro@zeniv.linux.org.uk>
CC: Markus Pargmann <mpa@pengutronix.de>
CC: Stefan Weinhuber <wein@de.ibm.com>
CC: Stefan Haberland <stefan.haberland@de.ibm.com>
CC: Sebastian Ott <sebott@linux.vnet.ibm.com>
CC: Fabian Frederick <fabf@skynet.be>
CC: Ming Lei <ming.lei@canonical.com>
CC: David Herrmann <dh.herrmann@gmail.com>
CC: Mike Galbraith <bitbucket@online.de>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: nbd-general@lists.sourceforge.net
CC: linux-s390@vger.kernel.org

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