Skip to content

L
linux
Switch branch/tag
  1. 27 May, 2020 21 commits
  3. 26 May, 2020 1 commit
    • Jiri Kosina's avatar
      block/floppy: fix contended case in floppy_queue_rq() · 263c6158
      Jiri Kosina authored 
      Since the switch of floppy driver to blk-mq, the contended (fdc_busy) case
in floppy_queue_rq() is not handled correctly.

In case we reach floppy_queue_rq() with fdc_busy set (i.e. with the floppy
locked due to another request still being in-flight), we put the request
on the list of requests and return BLK_STS_OK to the block core, without
actually scheduling delayed work / doing further processing of the
request. This means that processing of this request is postponed until
another request comes and passess uncontended.

Which in some cases might actually never happen and we keep waiting
indefinitely. The simple testcase is

	for i in `seq 1 2000`; do echo -en $i '\r'; blkid --info /dev/fd0 2> /dev/null; done

run in quemu. That reliably causes blkid eventually indefinitely hanging
in __floppy_read_block_0() waiting for completion, as the BIO callback
never happens, and no further IO is ever submitted on the (non-existent)
floppy device. This was observed reliably on qemu-emulated device.

Fix that by not queuing the request in the contended case, and return
BLK_STS_RESOURCE instead, so that blk core handles the request
rescheduling and let it pass properly non-contended later.

Fixes: a9f38e1d ("floppy: convert to blk-mq")
Cc: stable@vger.kernel.org
Tested-by: default avatarLibor Pechacek <lpechacek@suse.cz>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      263c6158
  5. 24 May, 2020 1 commit
  7. 21 May, 2020 14 commits
  9. 16 May, 2020 1 commit
  11. 13 May, 2020 2 commits
    • Jens Axboe's avatar
      Merge branch 'md-next' of... · 8fd2b980
      Jens Axboe authored 
      Merge branch 'md-next' of git://git.kernel.org/pub/scm/linux/kernel/git/song/md into for-5.8/drivers

Pull MD changes from Song.

* 'md-next' of git://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md/raid1: Replace zero-length array with flexible-array
  md: add a newline when printing parameter 'start_ro' by sysfs
  md: stop using ->queuedata
  md/raid1: release pending accounting for an I/O only after write-behind is also finished
  md: remove redundant memalloc scope API usage
  raid5: update code comment of scribble_alloc()
  raid5: remove gfp flags from scribble_alloc()
  md: use memalloc scope APIs in mddev_suspend()/mddev_resume()
  md: remove the extra line for ->hot_add_disk
  md: flush md_rdev_misc_wq for HOT_ADD_DISK case
  md: don't flush workqueue unconditionally in md_open
  md: add new workqueue for delete rdev
  md: add checkings before flush md_misc_wq
      8fd2b980
    • Gustavo A. R. Silva's avatar
      md/raid1: Replace zero-length array with flexible-array · 358369f0
      Gustavo A. R. Silva authored 
      The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: default avatarGustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
      358369f0
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7