Alexander reported mkswap on /dev/zram0 is failed if other process is
opening the block device file.

Step is as follows,

0. Reset the unused zram device.
1. Use a program that opens /dev/zram0 with O_RDWR and sleeps
   until killed.
2. While that program sleeps, echo the correct value to
   /sys/block/zram0/disksize.
3. Verify (e.g. in /proc/partitions) that the disk size is applied
   correctly. It is.
4. While that program still sleeps, attempt to mkswap /dev/zram0.
   This fails: mkswap: error: swap area needs to be at least 40 KiB

When I investigated, the size get by ioctl(fd, BLKGETSIZE64, xxx) on
mkswap to get a size of blockdev was zero although zram0 has right size by
2.

The reason is zram didn't revalidate disk after changing capacity so that
size of blockdev's inode is not uptodate until all of file is close.

This patch should fix the BUG.

Signed-off-by: Minchan Kim <minchan@kernel.org>
Reported-by: Alexander E. Patrakov <patrakov@gmail.com>
Tested-by: Alexander E. Patrakov <patrakov@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull block fixes from Jens Axboe:
 "A small collection of fixes/changes for the current series.  This
  contains:

   - Removal of dead code from Gu Zheng.

   - Revert of two bad fixes that went in earlier in this round, marking
     things as __init that were not purely used from init.

   - A fix for blk_mq_start_hw_queue() using the __blk_mq_run_hw_queue(),
     which could place us wrongly.  Make it use the non __ variant,
     which handles cases where we are called from the wrong CPU set.
     From me.

   - A fix for drbd, which allocates discard requests without room for
     the SCSI payload.  From Lars Ellenberg.

   - A fix for user-after-free in the blkcg code from Tejun.

   - Addition of limiting gaps in SG lists, if the hardware needs it.
     This is the last pre-req patch for blk-mq to enable the full NVMe
     conversion.  Could wait until 3.17, but it's simple enough so would
     be nice to have everything we need for the NVMe port in the 3.17
     release.  From me"

* 'for-linus' of git://git.kernel.dk/linux-block:
  drbd: fix NULL pointer deref in blk_add_request_payload
  blk-mq: blk_mq_start_hw_queue() should use blk_mq_run_hw_queue()
  block: add support for limiting gaps in SG lists
  bio: remove unused macro bip_vec_idx()
  Revert "block: add __init to elv_register"
  Revert "block: add __init to blkcg_policy_register"
  blkcg: fix use-after-free in __blkg_release_rcu() by making blkcg_gq refcnt an atomic_t
  floppy: format block0 read error message properly

Discards don't have any payload.
But the scsi layer still expects a bio_vec it can use internally,
see sd_setup_discard_cmnd() and blk_add_request_payload().

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

The following check in rbd_img_obj_request_submit()

    rbd_dev->parent_overlap <= obj_request->img_offset

allows the fall through to the non-layered write case even if both
parent_overlap and obj_request->img_offset belong to the same RADOS
object.  This leads to data corruption, because the area to the left of
parent_overlap ends up unconditionally zero-filled instead of being
populated with parent data.  Suppose we want to write 1M to offset 6M
of image bar, which is a clone of foo@snap; object_size is 4M,
parent_overlap is 5M:

    rbd_data.<id>.0000000000000001
     ---------------------|----------------------|------------
    | should be copyup'ed | should be zeroed out | write ...
     ---------------------|----------------------|------------
   4M                    5M                     6M
                    parent_overlap    obj_request->img_offset

4..5M should be copyup'ed from foo, yet it is zero-filled, just like
5..6M is.

Given that the only striping mode kernel client currently supports is
chunking (i.e. stripe_unit == object_size, stripe_count == 1), round
parent_overlap up to the next object boundary for the purposes of the
overlap check.

Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

Pull block fixes from Jens Axboe:
 "A smaller collection of fixes for the block core that would be nice to
  have in -rc2.  This pull request contains:

   - Fixes for races in the wait/wakeup logic used in blk-mq from
     Alexander.  No issues have been observed, but it is definitely a
     bit flakey currently.  Alternatively, we may drop the cyclic
     wakeups going forward, but that needs more testing.

   - Some cleanups from Christoph.

   - Fix for an oops in null_blk if queue_mode=1 and softirq completions
     are used.  From me.

   - A fix for a regression caused by the chunk size setting.  It
     inadvertently used max_hw_sectors instead of max_sectors, which is
     incorrect, and causes hangs on btrfs multi-disk setups (where hw
     sectors apparently isn't set).  From me.

   - Removal of WQ_POWER_EFFICIENT in the kblockd creation.  This was a
     recent addition as well, but it actually breaks blk-mq which relies
     on strict scheduling.  If the workqueue power_efficient mode is
     turned on, this breaks blk-mq.  From Matias.

   - null_blk module parameter description fix from Mike"

* 'for-linus' of git://git.kernel.dk/linux-block:
  blk-mq: bitmap tag: fix races in bt_get() function
  blk-mq: bitmap tag: fix race on blk_mq_bitmap_tags::wake_cnt
  blk-mq: bitmap tag: fix races on shared ::wake_index fields
  block: blk_max_size_offset() should check ->max_sectors
  null_blk: fix softirq completions for queue_mode == 1
  blk-mq: merge blk_mq_drain_queue and __blk_mq_drain_queue
  blk-mq: properly drain stopped queues
  block: remove WQ_POWER_EFFICIENT from kblockd
  null_blk: fix name and description of 'queue_mode' module parameter
  block: remove elv_abort_queue and blk_abort_flushes

In case reading of block 0 fails, line without trailing newline
is printed causing dmesg to look horrible.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Only blk-mq completions have payload attached to the request, for
request_fn mode we have stored it in req->special. This fixes an
oops with queue_mode=1 and softirq completions.

Signed-off-by: Jens Axboe <axboe@fb.com>

Pull NVMe update from Matthew Wilcox:
 "Mostly bugfixes again for the NVMe driver.  I'd like to call out the
  exported tracepoint in the block layer; I believe Keith has cleared
  this with Jens.

  We've had a few reports from people who're really pounding on NVMe
  devices at scale, hence the timeout changes (and new module
  parameters), hotplug cpu deadlock, tracepoints, and minor performance
  tweaks"

[ Jens hadn't seen that tracepoint thing, but is ok with it - it will
  end up going away when mq conversion happens ]

* git://git.infradead.org/users/willy/linux-nvme: (22 commits)
  NVMe: Fix START_STOP_UNIT Scsi->NVMe translation.
  NVMe: Use Log Page constants in SCSI emulation
  NVMe: Define Log Page constants
  NVMe: Fix hot cpu notification dead lock
  NVMe: Rename io_timeout to nvme_io_timeout
  NVMe: Use last bytes of f/w rev SCSI Inquiry
  NVMe: Adhere to request queue block accounting enable/disable
  NVMe: Fix nvme get/put queue semantics
  NVMe: Delete NVME_GET_FEAT_TEMP_THRESH
  NVMe: Make admin timeout a module parameter
  NVMe: Make iod bio timeout a parameter
  NVMe: Prevent possible NULL pointer dereference
  NVMe: Fix the buffer size passed in GetLogPage(CDW10.NUMD)
  NVMe: Update data structures for NVMe 1.2
  NVMe: Enable BUILD_BUG_ON checks
  NVMe: Update namespace and controller identify structures to the 1.1a spec
  NVMe: Flush with data support
  NVMe: Configure support for block flush
  NVMe: Add tracepoints
  NVMe: Protect against badly formatted CQEs
  ...

This patch contains several fixes for Scsi START_STOP_UNIT. The previous
code did not account for signed vs. unsigned arithmetic which resulted
in an invalid lowest power state caculation when the device only supports
1 power state.

The code for Power Condition == 2 (Idle) was not following the spec. The
spec calls for setting the device to specific power states, depending
upon Power Condition Modifier, without accounting for the number of
power states supported by the device.

The code for Power Condition == 3 (Standby) was using a hard-coded '0'
which is replaced with the macro POWER_STATE_0.

Signed-off-by: Dan McLeran <daniel.mcleran@intel.com>
Reviewed-by: Vishal Verma <vishal.l.verma@linux.intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>