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  1. 21 6月, 2019 2 次提交
  3. 20 6月, 2019 3 次提交
    • G
      block: drbd: no need to check return value of debugfs_create functions · d27e84a3
      由 Greg Kroah-Hartman 提交于 
      When calling debugfs functions, there is no need to ever check the
return value.  The function can work or not, but the code logic should
never do something different based on this.

Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: drbd-dev@lists.linbit.com
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      d27e84a3
    • C
      null_blk: remove duplicate 0 initialization · 8c54803b
      由 Chaitanya Kulkarni 提交于 
      In function null_add_dev() struct nullb *nullb member is allocated
using kzalloc_node() which returns 0red memory.

In function setup_queues() which is called from the null_add_dev(), on
successful queue allocation we set the nullb->nr_queues = 0 which is not
needed due to earlier use of kzalloc_node().
Signed-off-by: NChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      8c54803b
    • A
      floppy: fix harmless clang build warning · 2af47c10
      由 Arnd Bergmann 提交于 
      clang warns about unusual code in floppy.c that looks like it
was intended to be a bit mask operation, checking for a specific
bit in the UDP->cmos variable (FLOPPY1_TYPE expands to '4' on
ARM):

drivers/block/floppy.c:3902:17: error: use of logical '&&' with constant operand [-Werror,-Wconstant-logical-operand]
        if (!UDP->cmos && FLOPPY1_TYPE)
                       ^  ~~~~~~~~~~~~
drivers/block/floppy.c:3902:17: note: use '&' for a bitwise operation
        if (!UDP->cmos && FLOPPY1_TYPE)

The check here is redundant anyway, if FLOPPY1_TYPE is zero, then
assigning it to a zero UDP->cmos field does not change anything,
so removing the extra check here has no effect other than shutting
up the warning.

On x86, this will no longer read a hardware register, as the
FLOPPY1_TYPE macro is not expanded if UDP->cmos is already
zero, but the result is the same.

Cc: Robert Elliott <elliott@hpe.com>
Cc: Keith Busch <kbusch@kernel.org>
Link: https://patchwork.kernel.org/patch/10851841/Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      2af47c10
  5. 15 6月, 2019 9 次提交
  7. 14 6月, 2019 4 次提交
  9. 13 6月, 2019 5 次提交
    • G
      block/ps3vram: Use %llu to format sector_t after LBDAF removal · 1d0c0651
      由 Geert Uytterhoeven 提交于 
      The removal of CONFIG_LBDAF changed the type of sector_t from "unsigned
long" to "u64" aka "unsigned long long" on 64-bit platforms, leading to
a compiler warning regression:

    drivers/block/ps3vram.c: In function ‘ps3vram_probe’:
    drivers/block/ps3vram.c:770:23: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 4 has type ‘sector_t {aka long long unsigned int}’ [-Wformat=]

Fix this by using "%llu" instead.

Fixes: 72deb455 ("block: remove CONFIG_LBDAF")
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      1d0c0651
    • H
      libata: Extend quirks for the ST1000LM024 drives with NOLPM quirk · 31f6264e
      由 Hans de Goede 提交于 
      We've received a bugreport that using LPM with ST1000LM024 drives leads
to system lockups. So it seems that these models are buggy in more then
1 way. Add NOLPM quirk to the existing quirks entry for BROKEN_FPDMA_AA.

BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1571330
Cc: stable@vger.kernel.org
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NHans de Goede <hdegoede@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      31f6264e
    • C
      bcache: only set BCACHE_DEV_WB_RUNNING when cached device attached · 1f0ffa67
      由 Coly Li 提交于 
      When people set a writeback percent via sysfs file,
  /sys/block/bcache<N>/bcache/writeback_percent
current code directly sets BCACHE_DEV_WB_RUNNING to dc->disk.flags
and schedules kworker dc->writeback_rate_update.

If there is no cache set attached to, the writeback kernel thread is
not running indeed, running dc->writeback_rate_update does not make
sense and may cause NULL pointer deference when reference cache set
pointer inside update_writeback_rate().

This patch checks whether the cache set point (dc->disk.c) is NULL in
sysfs interface handler, and only set BCACHE_DEV_WB_RUNNING and
schedule dc->writeback_rate_update when dc->disk.c is not NULL (it
means the cache device is attached to a cache set).

This problem might be introduced from initial bcache commit, but
commit 3fd47bfe ("bcache: stop dc->writeback_rate_update properly")
changes part of the original code piece, so I add 'Fixes: 3fd47bfe'
to indicate from which commit this patch can be applied.

Fixes: 3fd47bfe ("bcache: stop dc->writeback_rate_update properly")
Reported-by: NBjørn Forsman <bjorn.forsman@gmail.com>
Signed-off-by: NColy Li <colyli@suse.de>
Reviewed-by: NBjørn Forsman <bjorn.forsman@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      1f0ffa67
    • C
      bcache: fix stack corruption by PRECEDING_KEY() · 31b90956
      由 Coly Li 提交于 
      Recently people report bcache code compiled with gcc9 is broken, one of
the buggy behavior I observe is that two adjacent 4KB I/Os should merge
into one but they don't. Finally it turns out to be a stack corruption
caused by macro PRECEDING_KEY().

See how PRECEDING_KEY() is defined in bset.h,
437 #define PRECEDING_KEY(_k)                                       \
438 ({                                                              \
439         struct bkey *_ret = NULL;                               \
440                                                                 \
441         if (KEY_INODE(_k) || KEY_OFFSET(_k)) {                  \
442                 _ret = &KEY(KEY_INODE(_k), KEY_OFFSET(_k), 0);  \
443                                                                 \
444                 if (!_ret->low)                                 \
445                         _ret->high--;                           \
446                 _ret->low--;                                    \
447         }                                                       \
448                                                                 \
449         _ret;                                                   \
450 })

At line 442, _ret points to address of a on-stack variable combined by
KEY(), the life range of this on-stack variable is in line 442-446,
once _ret is returned to bch_btree_insert_key(), the returned address
points to an invalid stack address and this address is overwritten in
the following called bch_btree_iter_init(). Then argument 'search' of
bch_btree_iter_init() points to some address inside stackframe of
bch_btree_iter_init(), exact address depends on how the compiler
allocates stack space. Now the stack is corrupted.

Fixes: 0eacac22 ("bcache: PRECEDING_KEY()")
Signed-off-by: NColy Li <colyli@suse.de>
Reviewed-by: NRolf Fokkens <rolf@rolffokkens.nl>
Reviewed-by: NPierre JUHEN <pierre.juhen@orange.fr>
Tested-by: NShenghui Wang <shhuiw@foxmail.com>
Tested-by: NPierre JUHEN <pierre.juhen@orange.fr>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Nix <nix@esperi.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      31b90956
    • C
      null_blk: remove duplicate check for report zone · 154085ff
      由 Chaitanya Kulkarni 提交于 
      This patch removes the check in the null_blk_zoned for report zone
command, where it checks for the dev-,>zoned before executing the report
zone.

The null_zone_report() function is a block_device operation callback
which is initialized in the null_blk_main.c and gets called as a part
of blkdev for report zone IOCTL (BLKREPORTZONE).

blkdev_ioctl()
blkdev_report_zones_ioctl()
        blkdev_report_zones()
                blk_report_zones()
                        disk->fops->report_zones()
                                nullb_zone_report();

The null_zone_report() will never get executed on the non-zoned block
device, in the non zoned block device blk_queue_is_zoned() will always
be false which is first check the blkdev_report_zones_ioctl()
before actual low level driver report zone callback is executed.

Here is the detailed scenario:-

1. modprobe null_blk
null_init
null_alloc_dev
        dev->zoned = 0
null_add_dev
        dev->zoned == 0
                so we don't set the q->limits.zoned = BLK_ZONED_HR

2. blkzone report /dev/nullb0

blkdev_ioctl()
blkdev_report_zones_ioctl()
        blk_queue_is_zoned()
                blk_queue_is_zoned
                        q->limits.zoned == 0
                        return false
        if (!blk_queue_is_zoned(q)) <--- true
                return -ENOTTY;
Reviewed-by: NDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: NBob Liu <bob.liu@oracle.com>
Signed-off-by: NChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      154085ff
  11. 12 6月, 2019 3 次提交
  13. 08 6月, 2019 2 次提交
    • R
      i2c: xiic: Add max_read_len quirk · 49b80958
      由 Robert Hancock 提交于 
      This driver does not support reading more than 255 bytes at once because
the register for storing the number of bytes to read is only 8 bits. Add
a max_read_len quirk to enforce this.

This was found when using this driver with the SFP driver, which was
previously reading all 256 bytes in the SFP EEPROM in one transaction.
This caused a bunch of hard-to-debug errors in the xiic driver since the
driver/logic was treating the number of bytes to read as zero.
Rejecting transactions that aren't supported at least allows the problem
to be diagnosed more easily.
Signed-off-by: NRobert Hancock <hancock@sedsystems.ca>
Reviewed-by: NMichal Simek <michal.simek@xilinx.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
      49b80958
    • H
      gpio: pca953x: hack to fix 24 bit gpio expanders · 3b00691c
      由 H. Nikolaus Schaller 提交于 
      24 bit expanders use REG_ADDR_AI in combination with register addressing. This
conflicts with regmap which takes this bit as part of the register number,
i.e. a second cache entry is defined for accessed with REG_ADDR_AI being
set although on the chip it is the same register as with REG_ADDR_AI being
cleared.

The problem was introduced by

	commit b32cecb4 ("gpio: pca953x: Extract the register address mangling to single function")

but only became visible by

	commit 8b9f9d4d ("regmap: verify if register is writeable before writing operations")

because before, the regmap size was effectively ignored and
pca953x_writeable_register() did know to ignore REG_ADDR_AI. Still, there
were two separate cache entries created.

Since the use of REG_ADDR_AI seems to be static we can work around this
issue by simply increasing the size of the regmap to cover the "virtual"
registers with REG_ADDR_AI being set. This only means that half of the
regmap buffer will be unused.
Reported-by: NH. Nikolaus Schaller <hns@goldelico.com>
Suggested-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NH. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
      3b00691c
  15. 07 6月, 2019 12 次提交
    • B
      drm/nouveau/secboot/gp10[2467]: support newer FW to fix SEC2 failures on some boards · ab4bec16
      由 Ben Skeggs 提交于 
      Some newer boards with these chipsets aren't compatible with the prior
version of the SEC2 FW, and fail to load as a result.

This newer FW is actually the one we already use on >=GP108.

Unfortunately, there are interface differences in GP108's FW, making it
impossible to simply move files around in linux-firmware to solve this.

We need to be able to keep compatibility with all linux-firmware/kernel
combinations, which means supporting both firmwares.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>
      ab4bec16
    • B
      drm/nouveau/secboot: enable loading of versioned LS PMU/SEC2 ACR msgqueue FW · 9352ce37
      由 Ben Skeggs 提交于 
      Some chipsets will be switching to updated SEC2 LS firmware, so we need to
plumb that through.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>
      9352ce37
    • B
      drm/nouveau/secboot: split out FW version-specific LS function pointers · 5f0f8b57
      由 Ben Skeggs 提交于 
      It's not enough to have per-falcon structures anymore, we have multiple
versions of some firmware now that have interface differences.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>
      5f0f8b57
    • B
      drm/nouveau/secboot: pass max supported FW version to LS load funcs · c26f3061
      由 Ben Skeggs 提交于 
      Will be passed to the FW loader function as an upper bound on the supported
FW version to attempt to load.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>
      c26f3061
    • B
      drm/nouveau/core: support versioned firmware loading · 475cf02b
      由 Ben Skeggs 提交于 
      We have a need for this now with updated SEC2 LS FW images that have an
incompatible interface from the previous version.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>
      475cf02b
    • B
      drm/nouveau/core: pass subdev into nvkm_firmware_get, rather than device · 8854eed1
      由 Ben Skeggs 提交于 
      It'd be nice to have FW loading debug messages to appear for the relevant
subsystem, when enabled.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>
      8854eed1
    • P
      vfio/mdev: Synchronize device create/remove with parent removal · 5715c4dd
      由 Parav Pandit 提交于 
      In following sequences, child devices created while removing mdev parent
device can be left out, or it may lead to race of removing half
initialized child mdev devices.

issue-1:
--------
       cpu-0                         cpu-1
       -----                         -----
                                  mdev_unregister_device()
                                    device_for_each_child()
                                      mdev_device_remove_cb()
                                        mdev_device_remove()
create_store()
  mdev_device_create()                   [...]
    device_add()
                                  parent_remove_sysfs_files()

/* BUG: device added by cpu-0
 * whose parent is getting removed
 * and it won't process this mdev.
 */

issue-2:
--------
Below crash is observed when user initiated remove is in progress
and mdev_unregister_driver() completes parent unregistration.

       cpu-0                         cpu-1
       -----                         -----
remove_store()
   mdev_device_remove()
   active = false;
                                  mdev_unregister_device()
                                  parent device removed.
   [...]
   parents->ops->remove()
 /*
  * BUG: Accessing invalid parent.
  */

This is similar race like create() racing with mdev_unregister_device().

BUG: unable to handle kernel paging request at ffffffffc0585668
PGD e8f618067 P4D e8f618067 PUD e8f61a067 PMD 85adca067 PTE 0
Oops: 0000 [#1] SMP PTI
CPU: 41 PID: 37403 Comm: bash Kdump: loaded Not tainted 5.1.0-rc6-vdevbus+ #6
Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b 08/09/2016
RIP: 0010:mdev_device_remove+0xfa/0x140 [mdev]
Call Trace:
 remove_store+0x71/0x90 [mdev]
 kernfs_fop_write+0x113/0x1a0
 vfs_write+0xad/0x1b0
 ksys_write+0x5a/0xe0
 do_syscall_64+0x5a/0x210
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Therefore, mdev core is improved as below to overcome above issues.

Wait for any ongoing mdev create() and remove() to finish before
unregistering parent device.
This continues to allow multiple create and remove to progress in
parallel for different mdev devices as most common case.
At the same time guard parent removal while parent is being accessed by
create() and remove() callbacks.
create()/remove() and unregister_device() are synchronized by the rwsem.

Refactor device removal code to mdev_device_remove_common() to avoid
acquiring unreg_sem of the parent.

Fixes: 7b96953b ("vfio: Mediated device Core driver")
Signed-off-by: NParav Pandit <parav@mellanox.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>
      5715c4dd
    • P
      vfio/mdev: Avoid creating sysfs remove file on stale device removal · 26c9e398
      由 Parav Pandit 提交于 
      If device is removal is initiated by two threads as below, mdev core
attempts to create a syfs remove file on stale device.
During this flow, below [1] call trace is observed.

     cpu-0                                    cpu-1
     -----                                    -----
  mdev_unregister_device()
    device_for_each_child
       mdev_device_remove_cb
          mdev_device_remove
                                       user_syscall
                                         remove_store()
                                           mdev_device_remove()
                                        [..]
   unregister device();
                                       /* not found in list or
                                        * active=false.
                                        */
                                          sysfs_create_file()
                                          ..Call trace

Now that mdev core follows correct device removal sequence of the linux
bus model, remove shouldn't fail in normal cases. If it fails, there is
no point of creating a stale file or checking for specific error status.

kernel: WARNING: CPU: 2 PID: 9348 at fs/sysfs/file.c:327
sysfs_create_file_ns+0x7f/0x90
kernel: CPU: 2 PID: 9348 Comm: bash Kdump: loaded Not tainted
5.1.0-rc6-vdevbus+ #6
kernel: Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b
08/09/2016
kernel: RIP: 0010:sysfs_create_file_ns+0x7f/0x90
kernel: Call Trace:
kernel: remove_store+0xdc/0x100 [mdev]
kernel: kernfs_fop_write+0x113/0x1a0
kernel: vfs_write+0xad/0x1b0
kernel: ksys_write+0x5a/0xe0
kernel: do_syscall_64+0x5a/0x210
kernel: entry_SYSCALL_64_after_hwframe+0x49/0xbe
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Signed-off-by: NParav Pandit <parav@mellanox.com>
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>
      26c9e398
    • M
      net: mvpp2: Use strscpy to handle stat strings · d37acd5a
      由 Maxime Chevallier 提交于 
      Use a safe strscpy call to copy the ethtool stat strings into the
relevant buffers, instead of a memcpy that will be accessing
out-of-bound data.

Fixes: 118d6298 ("net: mvpp2: add ethtool GOP statistics")
Signed-off-by: NMaxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      d37acd5a
    • M
      nvme-rdma: use dynamic dma mapping per command · 62f99b62
      由 Max Gurtovoy 提交于 
      Commit 87fd1253 ("nvme-rdma: remove redundant reference between
ib_device and tagset") caused a kernel panic when disconnecting from an
inaccessible controller (disconnect during re-connection).

--
nvme nvme0: Removing ctrl: NQN "testnqn1"
nvme_rdma: nvme_rdma_exit_request: hctx 0 queue_idx 1
BUG: unable to handle kernel paging request at 0000000080000228
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
...
Call Trace:
 blk_mq_exit_hctx+0x5c/0xf0
 blk_mq_exit_queue+0xd4/0x100
 blk_cleanup_queue+0x9a/0xc0
 nvme_rdma_destroy_io_queues+0x52/0x60 [nvme_rdma]
 nvme_rdma_shutdown_ctrl+0x3e/0x80 [nvme_rdma]
 nvme_do_delete_ctrl+0x53/0x80 [nvme_core]
 nvme_sysfs_delete+0x45/0x60 [nvme_core]
 kernfs_fop_write+0x105/0x180
 vfs_write+0xad/0x1a0
 ksys_write+0x5a/0xd0
 do_syscall_64+0x55/0x110
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fa215417154
--

The reason for this crash is accessing an already freed ib_device for
performing dma_unmap during exit_request commands. The root cause for
that is that during re-connection all the queues are destroyed and
re-created (and the ib_device is reference counted by the queues and
freed as well) but the tagset stays alive and all the DMA mappings (that
we perform in init_request) kept in the request context. The original
commit fixed a different bug that was introduced during bonding (aka nic
teaming) tests that for some scenarios change the underlying ib_device
and caused memory leakage and possible segmentation fault. This commit
is a complementary commit that also changes the wrong DMA mappings that
were saved in the request context and making the request sqe dma
mappings dynamic with the command lifetime (i.e. mapped in .queue_rq and
unmapped in .complete). It also fixes the above crash of accessing freed
ib_device during destruction of the tagset.

Fixes: 87fd1253 ("nvme-rdma: remove redundant reference between ib_device and tagset")
Reported-by: NJim Harris <james.r.harris@intel.com>
Suggested-by: NSagi Grimberg <sagi@grimberg.me>
Tested-by: NJim Harris <james.r.harris@intel.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMax Gurtovoy <maxg@mellanox.com>
Signed-off-by: NSagi Grimberg <sagi@grimberg.me>
      62f99b62
    • J
      nvme: Fix u32 overflow in the number of namespace list calculation · c8e8c77b
      由 Jaesoo Lee 提交于 
      The Number of Namespaces (nn) field in the identify controller data structure is
defined as u32 and the maximum allowed value in NVMe specification is
0xFFFFFFFEUL. This change fixes the possible overflow of the DIV_ROUND_UP()
operation used in nvme_scan_ns_list() by casting the nn to u64.
Signed-off-by: NJaesoo Lee <jalee@purestorage.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NSagi Grimberg <sagi@grimberg.me>
      c8e8c77b
    • P
      vfio/mdev: Improve the create/remove sequence · 522ecce0
      由 Parav Pandit 提交于 
      This patch addresses below two issues and prepares the code to address
3rd issue listed below.

1. mdev device is placed on the mdev bus before it is created in the
vendor driver. Once a device is placed on the mdev bus without creating
its supporting underlying vendor device, mdev driver's probe() gets
triggered.  However there isn't a stable mdev available to work on.

   create_store()
     mdev_create_device()
       device_register()
          ...
         vfio_mdev_probe()
        [...]
        parent->ops->create()
          vfio_ap_mdev_create()
            mdev_set_drvdata(mdev, matrix_mdev);
            /* Valid pointer set above */

Due to this way of initialization, mdev driver who wants to use the mdev,
doesn't have a valid mdev to work on.

2. Current creation sequence is,
   parent->ops_create()
   groups_register()

Remove sequence is,
   parent->ops->remove()
   groups_unregister()

However, remove sequence should be exact mirror of creation sequence.
Once this is achieved, all users of the mdev will be terminated first
before removing underlying vendor device.
(Follow standard linux driver model).
At that point vendor's remove() ops shouldn't fail because taking the
device off the bus should terminate any usage.

3. When remove operation fails, mdev sysfs removal attempts to add the
file back on already removed device. Following call trace [1] is observed.

[1] call trace:
kernel: WARNING: CPU: 2 PID: 9348 at fs/sysfs/file.c:327 sysfs_create_file_ns+0x7f/0x90
kernel: CPU: 2 PID: 9348 Comm: bash Kdump: loaded Not tainted 5.1.0-rc6-vdevbus+ #6
kernel: Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b 08/09/2016
kernel: RIP: 0010:sysfs_create_file_ns+0x7f/0x90
kernel: Call Trace:
kernel: remove_store+0xdc/0x100 [mdev]
kernel: kernfs_fop_write+0x113/0x1a0
kernel: vfs_write+0xad/0x1b0
kernel: ksys_write+0x5a/0xe0
kernel: do_syscall_64+0x5a/0x210
kernel: entry_SYSCALL_64_after_hwframe+0x49/0xbe

Therefore, mdev core is improved in following ways.

1. Split the device registration/deregistration sequence so that some
things can be done between initialization of the device and hooking it
up to the bus respectively after deregistering it from the bus but
before giving up our final reference.
In particular, this means invoking the ->create() and ->remove()
callbacks in those new windows. This gives the vendor driver an
initialized mdev device to work with during creation.
At the same time, a bus driver who wish to bind to mdev driver also
gets initialized mdev device.

This follows standard Linux kernel bus and device model.

2. During remove flow, first remove the device from the bus. This
ensures that any bus specific devices are removed.
Once device is taken off the mdev bus, invoke remove() of mdev
from the vendor driver.

3. The driver core device model provides way to register and auto
unregister the device sysfs attribute groups at dev->groups.
Make use of dev->groups to let core create the groups and eliminate
code to avoid explicit groups creation and removal.

To ensure, that new sequence is solid, a below stack dump of a
process is taken who attempts to remove the device while device is in
use by vfio driver and user application.
This stack dump validates that vfio driver guards against such device
removal when device is in use.

 cat /proc/21962/stack
[<0>] vfio_del_group_dev+0x216/0x3c0 [vfio]
[<0>] mdev_remove+0x21/0x40 [mdev]
[<0>] device_release_driver_internal+0xe8/0x1b0
[<0>] bus_remove_device+0xf9/0x170
[<0>] device_del+0x168/0x350
[<0>] mdev_device_remove_common+0x1d/0x50 [mdev]
[<0>] mdev_device_remove+0x8c/0xd0 [mdev]
[<0>] remove_store+0x71/0x90 [mdev]
[<0>] kernfs_fop_write+0x113/0x1a0
[<0>] vfs_write+0xad/0x1b0
[<0>] ksys_write+0x5a/0xe0
[<0>] do_syscall_64+0x5a/0x210
[<0>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[<0>] 0xffffffffffffffff

This prepares the code to eliminate calling device_create_file() in
subsequent patch.
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Signed-off-by: NParav Pandit <parav@mellanox.com>
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>
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