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  1. 27 May, 2020 12 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 11 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
    • Xiongfeng Wang's avatar
      md: add a newline when printing parameter 'start_ro' by sysfs · 3f99980c
      Xiongfeng Wang authored 
      Add a missing newline when printing module parameter 'start_ro' by
sysfs.
Signed-off-by: default avatarXiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
      3f99980c
    • Christoph Hellwig's avatar
      md: stop using ->queuedata · e4fc5a74
      Christoph Hellwig authored 
      Pointer to mddev is already available in private_data.
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
      e4fc5a74
    • David Jeffery's avatar
      md/raid1: release pending accounting for an I/O only after write-behind is also finished · c91114c2
      David Jeffery authored 
      When using RAID1 and write-behind, md can deadlock when errors occur. With
write-behind, r1bio structs can be accounted by raid1 as queued but not
counted as pending. The pending count is dropped when the original bio is
returned complete but write-behind for the r1bio may still be active.

This breaks the accounting used in some conditions to know when the raid1
md device has reached an idle state. It can result in calls to
freeze_array deadlocking. freeze_array will never complete from a negative
"unqueued" value being calculated due to a queued count larger than the
pending count.

To properly account for write-behind, move the call to allow_barrier from
call_bio_endio to raid_end_bio_io. When using write-behind, md can call
call_bio_endio before all write-behind I/O is complete. Using
raid_end_bio_io for the point to call allow_barrier will release the
pending count at a point where all I/O for an r1bio, even write-behind, is
done.
Signed-off-by: default avatarDavid Jeffery <djeffery@redhat.com>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
      c91114c2
    • Coly Li's avatar
      md: remove redundant memalloc scope API usage · 3024ba2d
      Coly Li authored 
      In mddev_create_serial_pool(), memalloc scope APIs memalloc_noio_save()
and memalloc_noio_restore() are used when allocating memory by calling
mempool_create_kmalloc_pool(). After adding the memalloc scope APIs in
raid array suspend context, it is unncessary to explicitly call them
around mempool_create_kmalloc_pool() any longer.

This patch removes the redundant memalloc scope APIs in
mddev_create_serial_pool().
Signed-off-by: default avatarColy Li <colyli@suse.de>
Cc: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
      3024ba2d
    • Coly Li's avatar
      raid5: update code comment of scribble_alloc() · 7f8a30e5
      Coly Li authored 
      Code comments of scribble_alloc() is outdated for a while. This patch
update the comments in function header for the new parameter list.
Suggested-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarColy Li <colyli@suse.de>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
      7f8a30e5
    • Coly Li's avatar
      raid5: remove gfp flags from scribble_alloc() · ba54d4d4
      Coly Li authored 
      Using GFP_NOIO flag to call scribble_alloc() from resize_chunk() does
not have the expected behavior. kvmalloc_array() inside scribble_alloc()
which receives the GFP_NOIO flag will eventually call kmalloc_node() to
allocate physically continuous pages.

Now we have memalloc scope APIs in mddev_suspend()/mddev_resume() to
prevent memory reclaim I/Os during raid array suspend context, calling
to kvmalloc_array() with GFP_KERNEL flag may avoid deadlock of recursive
I/O as expected.

This patch removes the useless gfp flags from parameters list of
scribble_alloc(), and call kvmalloc_array() with GFP_KERNEL flag. The
incorrect GFP_NOIO flag does not exist anymore.

Fixes: b330e6a4 ("md: convert to kvmalloc")
Suggested-by: default avatarMichal Hocko <mhocko@suse.com>
Signed-off-by: default avatarColy Li <colyli@suse.de>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
      ba54d4d4
    • Coly Li's avatar
      md: use memalloc scope APIs in mddev_suspend()/mddev_resume() · 78f57ef9
      Coly Li authored 
      In raid5.c:resize_chunk(), scribble_alloc() is called with GFP_NOIO
flag, then it is sent into kvmalloc_array() inside scribble_alloc().

The problem is kvmalloc_array() eventually calls kvmalloc_node() which
does not accept non GFP_KERNEL compatible flag like GFP_NOIO, then
kmalloc_node() is called indeed to allocate physically continuous
pages. When system memory is under heavy pressure, and the requesting
size is large, there is high probability that allocating continueous
pages will fail.

But simply using GFP_KERNEL flag to call kvmalloc_array() is also
progblematic. In the code path where scribble_alloc() is called, the
raid array is suspended, if kvmalloc_node() triggers memory reclaim I/Os
and such I/Os go back to the suspend raid array, deadlock will happen.

What is desired here is to allocate non-physically (a.k.a virtually)
continuous pages and avoid memory reclaim I/Os. Michal Hocko suggests
to use the mmealloc sceope APIs to restrict memory reclaim I/O in
allocating context, specifically to call memalloc_noio_save() when
suspend the raid array and to call memalloc_noio_restore() when
resume the raid array.

This patch adds the memalloc scope APIs in mddev_suspend() and
mddev_resume(), to restrict memory reclaim I/Os during the raid array
is suspended. The benifit of adding the memalloc scope API in the
unified entry point mddev_suspend()/mddev_resume() is, no matter which
md raid array type (personality), we are sure the deadlock by recursive
memory reclaim I/O won't happen on the suspending context.

Please notice that the memalloc scope APIs only take effect on the raid
array suspending context, if the memory allocation is from another new
created kthread after raid array suspended, the recursive memory reclaim
I/Os won't be restricted. The mddev_suspend()/mddev_resume() entries are
used for the critical section where the raid metadata is modifying,
creating a kthread to allocate memory inside the critical section is
queer and very probably being buggy.

Fixes: b330e6a4 ("md: convert to kvmalloc")
Suggested-by: default avatarMichal Hocko <mhocko@suse.com>
Signed-off-by: default avatarColy Li <colyli@suse.de>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
      78f57ef9
    • Guoqing Jiang's avatar
      md: remove the extra line for ->hot_add_disk · 3f79cc22
      Guoqing Jiang authored 
      It is not not necessary to add a newline for them since they don't exceed
80 characters, and it is not intutive to distinguish ->hot_add_disk() from
hot_add_disk() too.
Signed-off-by: default avatarGuoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
      3f79cc22
    • Guoqing Jiang's avatar
      md: flush md_rdev_misc_wq for HOT_ADD_DISK case · 78b990cf
      Guoqing Jiang authored 
      Since rdev->kobj is removed asynchronously, it is possible that the
rdev->kobj still exists when try to add the rdev again after rdev
is removed. But this path md_ioctl (HOT_ADD_DISK) -> hot_add_disk
-> bind_rdev_to_array missed it.
Signed-off-by: default avatarGuoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
      78b990cf
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