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Subject[PATCH v1 0/7] block: reread partitions changes and fix for loop
Date
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.

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 | 20 ++++------------
include/linux/fs.h | 3 +++
6 files changed, 79 insertions(+), 34 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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