linux-kernel - [PATCH v2 0/7] block: reread partitions changes and fix for loop

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Date:	Sat, 11 Apr 2015 19:30:06 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Tejun Heo <tj@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jarod Wilson <jarod@...hat.com>,
	David Herrmann <dh.herrmann@...il.com>,
	Markus Pargmann <mpa@...gutronix.de>,
	nbd-general@...ts.sourceforge.net,
	Stefan Haberland <stefan.haberland@...ibm.com>,
	Sebastian Ott <sebott@...ux.vnet.ibm.com>,
	Fabian Frederick <fabf@...net.be>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-s390@...r.kernel.org
Subject: [PATCH v2 0/7] block: reread partitions changes and fix for loop

Hi Guys,

Recently there are several reports about loop partition scanning
failure[1][2].

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 __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.

V2:
	- only print debug message in case of error (7/7)
	- add tested-by, acked-by

V1:
	- introduce __blkdev_reread_part(), and use lockdep_assert_held()(1/7)
	- replace lo_open_mutex with atomic reference count, plus freezing queue(2/7)
	- add comment about detecting release path(3/7)
	- remove dead code in dasd(7/7)

 block/ioctl.c                   |   37 +++++++++++++++++++++++++----
 drivers/block/loop.c            |   49 +++++++++++++++++++++++++++++----------
 drivers/block/loop.h            |    2 +-
 drivers/block/nbd.c             |    2 +-
 drivers/s390/block/dasd_genhd.c |   19 ++++-----------
 include/linux/fs.h              |    3 +++
 6 files changed, 79 insertions(+), 33 deletions(-)

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

Thanks,
Ming Lei

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