linux-toradex.git/drivers/block/loop.c, branch v6.3-rc1 Linux kernel for Apalis and Colibri modules loop: loop_set_status_from_info() check before assignment 2023-02-23T03:43:09+00:00 Zhong Jinghua zhongjinghua@huawei.com 2023-02-21T09:50:27+00:00 9f6ad5d533d1c71e51bdd06a5712c4fbc8768dfa In loop_set_status_from_info(), lo->lo_offset and lo->lo_sizelimit should be checked before reassignment, because if an overflow error occurs, the original correct value will be changed to the wrong value, and it will not be changed back. More, the original patch did not solve the problem, the value was set and ioctl returned an error, but the subsequent io used the value in the loop driver, which still caused an alarm: loop_handle_cmd do_req_filebacked loff_t pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset; lo_rw_aio cmd->iocb.ki_pos = pos Fixes: c490a0b5a4f3 ("loop: Check for overflow while configuring loop") Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com> Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com> Link: https://lore.kernel.org/r/20230221095027.3656193-1-zhongjinghua@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk> 
In loop_set_status_from_info(), lo->lo_offset and lo->lo_sizelimit should
be checked before reassignment, because if an overflow error occurs, the
original correct value will be changed to the wrong value, and it will not
be changed back.

More, the original patch did not solve the problem, the value was set and
ioctl returned an error, but the subsequent io used the value in the loop
driver, which still caused an alarm:

loop_handle_cmd
 do_req_filebacked
  loff_t pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset;
  lo_rw_aio
   cmd->iocb.ki_pos = pos

Fixes: c490a0b5a4f3 ("loop: Check for overflow while configuring loop")
Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20230221095027.3656193-1-zhongjinghua@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
loop: Improve the hw_queue_depth kernel module parameter implementation 2023-02-01T15:16:11+00:00 Bart Van Assche bvanassche@acm.org 2023-01-30T21:13:47+00:00 e152a05fa054170c05f1d5e04e93e2e75ea11405 Make the following minor changes which were reported by colleagues while reviewing this code: - Remove the parentheses from around the LOOP_DEFAULT_HW_Q_DEPTH definition since these are superfluous. - Accept other number formats than decimal, e.g. hexadecimal. - Do not set hw_queue_depth to an out-of-range value, even if that value won't be used. - Use the LOOP_DEFAULT_HW_Q_DEPTH macro in the kernel module parameter description to prevent that the description gets out of sync. This patch has been tested as follows: # modprobe -r loop # modprobe loop hw_queue_depth=-1 modprobe: ERROR: could not insert 'loop': Invalid argument # modprobe loop hw_queue_depth=0 modprobe: ERROR: could not insert 'loop': Invalid argument # modprobe loop hw_queue_depth=1; cat /sys/module/loop/parameters/hw_queue_depth 1 # modprobe -r loop; modprobe loop; cat /sys/module/loop/parameters/hw_queue_depth hw_queue_depth=0x10 16 # modprobe -r loop; modprobe loop; cat /sys/module/loop/parameters/hw_queue_depth hw_queue_depth=128 128 # modprobe -r loop; modprobe loop hw_queue_depth=129; cat /sys/module/loop/parameters/hw_queue_depth 129 # modprobe -r loop; modprobe loop hw_queue_depth=$((1<<32)) modprobe: ERROR: could not insert 'loop': Numerical result out of range See also commit ef44c50837ab ("loop: allow user to set the queue depth"). Cc: Chaitanya Kulkarni <kch@nvidia.com> Cc: Himanshu Madhani <himanshu.madhani@oracle.com> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com> Link: https://lore.kernel.org/r/20230130211347.832110-1-bvanassche@acm.org Signed-off-by: Jens Axboe <axboe@kernel.dk> 
Make the following minor changes which were reported by colleagues
while reviewing this code:
- Remove the parentheses from around the LOOP_DEFAULT_HW_Q_DEPTH
  definition since these are superfluous.
- Accept other number formats than decimal, e.g. hexadecimal.
- Do not set hw_queue_depth to an out-of-range value, even if that value
  won't be used.
- Use the LOOP_DEFAULT_HW_Q_DEPTH macro in the kernel module parameter
  description to prevent that the description gets out of sync.

This patch has been tested as follows:

 # modprobe -r loop
 # modprobe loop hw_queue_depth=-1
 modprobe: ERROR: could not insert 'loop': Invalid argument
 # modprobe loop hw_queue_depth=0
 modprobe: ERROR: could not insert 'loop': Invalid argument
 # modprobe loop hw_queue_depth=1; cat /sys/module/loop/parameters/hw_queue_depth
 1
 # modprobe -r loop; modprobe loop; cat /sys/module/loop/parameters/hw_queue_depth hw_queue_depth=0x10
 16
 # modprobe -r loop; modprobe loop; cat /sys/module/loop/parameters/hw_queue_depth hw_queue_depth=128
 128
 # modprobe -r loop; modprobe loop hw_queue_depth=129; cat /sys/module/loop/parameters/hw_queue_depth
 129
 # modprobe -r loop; modprobe loop hw_queue_depth=$((1<<32))
 modprobe: ERROR: could not insert 'loop': Numerical result out of range

See also commit ef44c50837ab ("loop: allow user to set the queue
depth").

Cc: Chaitanya Kulkarni <kch@nvidia.com>
Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20230130211347.832110-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
treewide: Convert del_timer*() to timer_shutdown*() 2022-12-25T21:38:09+00:00 Steven Rostedt (Google) rostedt@goodmis.org 2022-12-20T18:45:19+00:00 292a089d78d3e2f7944e60bb897c977785a321e3 Due to several bugs caused by timers being re-armed after they are shutdown and just before they are freed, a new state of timers was added called "shutdown". After a timer is set to this state, then it can no longer be re-armed. The following script was run to find all the trivial locations where del_timer() or del_timer_sync() is called in the same function that the object holding the timer is freed. It also ignores any locations where the timer->function is modified between the del_timer*() and the free(), as that is not considered a "trivial" case. This was created by using a coccinelle script and the following commands: $ cat timer.cocci @@ expression ptr, slab; identifier timer, rfield; @@ ( - del_timer(&ptr->timer); + timer_shutdown(&ptr->timer); | - del_timer_sync(&ptr->timer); + timer_shutdown_sync(&ptr->timer); ) ... when strict when != ptr->timer ( kfree_rcu(ptr, rfield); | kmem_cache_free(slab, ptr); | kfree(ptr); ) $ spatch timer.cocci . > /tmp/t.patch $ patch -p1 < /tmp/t.patch Link: https://lore.kernel.org/lkml/20221123201306.823305113@linutronix.de/ Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Acked-by: Pavel Machek <pavel@ucw.cz> [ LED ] Acked-by: Kalle Valo <kvalo@kernel.org> [ wireless ] Acked-by: Paolo Abeni <pabeni@redhat.com> [ networking ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Due to several bugs caused by timers being re-armed after they are
shutdown and just before they are freed, a new state of timers was added
called "shutdown".  After a timer is set to this state, then it can no
longer be re-armed.

The following script was run to find all the trivial locations where
del_timer() or del_timer_sync() is called in the same function that the
object holding the timer is freed.  It also ignores any locations where
the timer->function is modified between the del_timer*() and the free(),
as that is not considered a "trivial" case.

This was created by using a coccinelle script and the following
commands:

    $ cat timer.cocci
    @@
    expression ptr, slab;
    identifier timer, rfield;
    @@
    (
    -       del_timer(&ptr->timer);
    +       timer_shutdown(&ptr->timer);
    |
    -       del_timer_sync(&ptr->timer);
    +       timer_shutdown_sync(&ptr->timer);
    )
      ... when strict
          when != ptr->timer
    (
            kfree_rcu(ptr, rfield);
    |
            kmem_cache_free(slab, ptr);
    |
            kfree(ptr);
    )

    $ spatch timer.cocci . > /tmp/t.patch
    $ patch -p1 < /tmp/t.patch

Link: https://lore.kernel.org/lkml/20221123201306.823305113@linutronix.de/
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Pavel Machek <pavel@ucw.cz> [ LED ]
Acked-by: Kalle Valo <kvalo@kernel.org> [ wireless ]
Acked-by: Paolo Abeni <pabeni@redhat.com> [ networking ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
loop: Fix the max_loop commandline argument treatment when it is set to 0 2022-12-14T17:55:20+00:00 Isaac J. Manjarres isaacmanjarres@google.com 2022-12-08T21:29:01+00:00 85c50197716c60fe57f411339c579462e563ac57 Currently, the max_loop commandline argument can be used to specify how many loop block devices are created at init time. If it is not specified on the commandline, CONFIG_BLK_DEV_LOOP_MIN_COUNT loop block devices will be created. The max_loop commandline argument can be used to override the value of CONFIG_BLK_DEV_LOOP_MIN_COUNT. However, when max_loop is set to 0 through the commandline, the current logic treats it as if it had not been set, and creates CONFIG_BLK_DEV_LOOP_MIN_COUNT devices anyway. Fix this by starting max_loop off as set to CONFIG_BLK_DEV_LOOP_MIN_COUNT. This preserves the intended behavior of creating CONFIG_BLK_DEV_LOOP_MIN_COUNT loop block devices if the max_loop commandline parameter is not specified, and allowing max_loop to be respected for all values, including 0. This allows environments that can create all of their required loop block devices on demand to not have to unnecessarily preallocate loop block devices. Fixes: 732850827450 ("remove artificial software max_loop limit") Cc: stable@vger.kernel.org Cc: Ken Chen <kenchen@google.com> Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com> Link: https://lore.kernel.org/r/20221208212902.765781-1-isaacmanjarres@google.com Signed-off-by: Jens Axboe <axboe@kernel.dk> 
Currently, the max_loop commandline argument can be used to specify how
many loop block devices are created at init time. If it is not
specified on the commandline, CONFIG_BLK_DEV_LOOP_MIN_COUNT loop block
devices will be created.

The max_loop commandline argument can be used to override the value of
CONFIG_BLK_DEV_LOOP_MIN_COUNT. However, when max_loop is set to 0
through the commandline, the current logic treats it as if it had not
been set, and creates CONFIG_BLK_DEV_LOOP_MIN_COUNT devices anyway.

Fix this by starting max_loop off as set to CONFIG_BLK_DEV_LOOP_MIN_COUNT.
This preserves the intended behavior of creating
CONFIG_BLK_DEV_LOOP_MIN_COUNT loop block devices if the max_loop
commandline parameter is not specified, and allowing max_loop to
be respected for all values, including 0.

This allows environments that can create all of their required loop
block devices on demand to not have to unnecessarily preallocate loop
block devices.

Fixes: 732850827450 ("remove artificial software max_loop limit")
Cc: stable@vger.kernel.org
Cc: Ken Chen <kenchen@google.com>
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>
Link: https://lore.kernel.org/r/20221208212902.765781-1-isaacmanjarres@google.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
use less confusing names for iov_iter direction initializers 2022-11-25T18:01:55+00:00 Al Viro viro@zeniv.linux.org.uk 2022-09-16T00:25:47+00:00 de4eda9de2d957ef2d6a8365a01e26a435e958cb READ/WRITE proved to be actively confusing - the meanings are "data destination, as used with read(2)" and "data source, as used with write(2)", but people keep interpreting those as "we read data from it" and "we write data to it", i.e. exactly the wrong way. Call them ITER_DEST and ITER_SOURCE - at least that is harder to misinterpret... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> 
READ/WRITE proved to be actively confusing - the meanings are
"data destination, as used with read(2)" and "data source, as
used with write(2)", but people keep interpreting those as
"we read data from it" and "we write data to it", i.e. exactly
the wrong way.

Call them ITER_DEST and ITER_SOURCE - at least that is harder
to misinterpret...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
loop: Check for overflow while configuring loop 2022-08-24T12:52:52+00:00 Siddh Raman Pant code@siddh.me 2022-08-23T16:08:10+00:00 c490a0b5a4f36da3918181a8acdc6991d967c5f3 The userspace can configure a loop using an ioctl call, wherein a configuration of type loop_config is passed (see lo_ioctl()'s case on line 1550 of drivers/block/loop.c). This proceeds to call loop_configure() which in turn calls loop_set_status_from_info() (see line 1050 of loop.c), passing &config->info which is of type loop_info64*. This function then sets the appropriate values, like the offset. loop_device has lo_offset of type loff_t (see line 52 of loop.c), which is typdef-chained to long long, whereas loop_info64 has lo_offset of type __u64 (see line 56 of include/uapi/linux/loop.h). The function directly copies offset from info to the device as follows (See line 980 of loop.c): lo->lo_offset = info->lo_offset; This results in an overflow, which triggers a warning in iomap_iter() due to a call to iomap_iter_done() which has: WARN_ON_ONCE(iter->iomap.offset > iter->pos); Thus, check for negative value during loop_set_status_from_info(). Bug report: https://syzkaller.appspot.com/bug?id=c620fe14aac810396d3c3edc9ad73848bf69a29e Reported-and-tested-by: syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Siddh Raman Pant <code@siddh.me> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220823160810.181275-1-code@siddh.me Signed-off-by: Jens Axboe <axboe@kernel.dk> 
The userspace can configure a loop using an ioctl call, wherein
a configuration of type loop_config is passed (see lo_ioctl()'s
case on line 1550 of drivers/block/loop.c). This proceeds to call
loop_configure() which in turn calls loop_set_status_from_info()
(see line 1050 of loop.c), passing &config->info which is of type
loop_info64*. This function then sets the appropriate values, like
the offset.

loop_device has lo_offset of type loff_t (see line 52 of loop.c),
which is typdef-chained to long long, whereas loop_info64 has
lo_offset of type __u64 (see line 56 of include/uapi/linux/loop.h).

The function directly copies offset from info to the device as
follows (See line 980 of loop.c):
	lo->lo_offset = info->lo_offset;

This results in an overflow, which triggers a warning in iomap_iter()
due to a call to iomap_iter_done() which has:
	WARN_ON_ONCE(iter->iomap.offset > iter->pos);

Thus, check for negative value during loop_set_status_from_info().

Bug report: https://syzkaller.appspot.com/bug?id=c620fe14aac810396d3c3edc9ad73848bf69a29e

Reported-and-tested-by: syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Siddh Raman Pant <code@siddh.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220823160810.181275-1-code@siddh.me
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block: remove blk_cleanup_disk 2022-06-28T12:33:15+00:00 Christoph Hellwig hch@lst.de 2022-06-19T06:05:52+00:00 8b9ab62662048a3274361c7e5f64037c2c133e2c blk_cleanup_disk is nothing but a trivial wrapper for put_disk now, so remove it. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Link: https://lore.kernel.org/r/20220619060552.1850436-7-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk> 
blk_cleanup_disk is nothing but a trivial wrapper for put_disk now,
so remove it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20220619060552.1850436-7-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block: simplify disk shutdown 2022-06-28T12:30:26+00:00 Christoph Hellwig hch@lst.de 2022-06-19T06:05:51+00:00 6f8191fdf41d3a53cc1d63fe2234e812c55a0092 Set the queue dying flag and call blk_mq_exit_queue from del_gendisk for all disks that do not have separately allocated queues, and thus remove the need to call blk_cleanup_queue for them. Rename blk_cleanup_disk to blk_mq_destroy_queue to make it clear that this function is intended only for separately allocated blk-mq queues. This saves an extra queue freeze for devices without a separately allocated queue. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Link: https://lore.kernel.org/r/20220619060552.1850436-6-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk> 
Set the queue dying flag and call blk_mq_exit_queue from del_gendisk for
all disks that do not have separately allocated queues, and thus remove
the need to call blk_cleanup_queue for them.

Rename blk_cleanup_disk to blk_mq_destroy_queue to make it clear that
this function is intended only for separately allocated blk-mq queues.

This saves an extra queue freeze for devices without a separately
allocated queue.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20220619060552.1850436-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Merge tag 'for-5.19/drivers-2022-06-02' of git://git.kernel.dk/linux-block 2022-06-03T17:25:56+00:00 Linus Torvalds torvalds@linux-foundation.org 2022-06-03T17:25:56+00:00 78c6499c92090d0fd1ddd1684fc3a5dc41d98c92 Pull more block driver updates from Jens Axboe: "A collection of stragglers that were late on sending in their changes and just followup fixes. - NVMe fixes pull request via Christoph: - set controller enable bit in a separate write (Niklas Cassel) - disable namespace identifiers for the MAXIO MAP1001 (Christoph) - fix a comment typo (Julia Lawall)" - MD fixes pull request via Song: - Remove uses of bdevname (Christoph Hellwig) - Bug fixes (Guoqing Jiang, and Xiao Ni) - bcache fixes series (Coly) - null_blk zoned write fix (Damien) - nbd fixes (Yu, Zhang) - Fix for loop partition scanning (Christoph)" * tag 'for-5.19/drivers-2022-06-02' of git://git.kernel.dk/linux-block: (23 commits) block: null_blk: Fix null_zone_write() nvmet: fix typo in comment nvme: set controller enable bit in a separate write nvme-pci: disable namespace identifiers for the MAXIO MAP1001 bcache: avoid unnecessary soft lockup in kworker update_writeback_rate() nbd: use pr_err to output error message nbd: fix possible overflow on 'first_minor' in nbd_dev_add() nbd: fix io hung while disconnecting device nbd: don't clear 'NBD_CMD_INFLIGHT' flag if request is not completed nbd: fix race between nbd_alloc_config() and module removal nbd: call genl_unregister_family() first in nbd_cleanup() md: bcache: check the return value of kzalloc() in detached_dev_do_request() bcache: memset on stack variables in bch_btree_check() and bch_sectors_dirty_init() block, loop: support partitions without scanning bcache: avoid journal no-space deadlock by reserving 1 journal bucket bcache: remove incremental dirty sector counting for bch_sectors_dirty_init() bcache: improve multithreaded bch_sectors_dirty_init() bcache: improve multithreaded bch_btree_check() md: fix double free of io_acct_set bioset md: Don't set mddev private to NULL in raid0 pers->free ... 
Pull more block driver updates from Jens Axboe:
 "A collection of stragglers that were late on sending in their changes
  and just followup fixes.

   - NVMe fixes pull request via Christoph:
       - set controller enable bit in a separate write (Niklas Cassel)
       - disable namespace identifiers for the MAXIO MAP1001 (Christoph)
       - fix a comment typo (Julia Lawall)"

   - MD fixes pull request via Song:
       - Remove uses of bdevname (Christoph Hellwig)
       - Bug fixes (Guoqing Jiang, and Xiao Ni)

   - bcache fixes series (Coly)

   - null_blk zoned write fix (Damien)

   - nbd fixes (Yu, Zhang)

   - Fix for loop partition scanning (Christoph)"

* tag 'for-5.19/drivers-2022-06-02' of git://git.kernel.dk/linux-block: (23 commits)
  block: null_blk: Fix null_zone_write()
  nvmet: fix typo in comment
  nvme: set controller enable bit in a separate write
  nvme-pci: disable namespace identifiers for the MAXIO MAP1001
  bcache: avoid unnecessary soft lockup in kworker update_writeback_rate()
  nbd: use pr_err to output error message
  nbd: fix possible overflow on 'first_minor' in nbd_dev_add()
  nbd: fix io hung while disconnecting device
  nbd: don't clear 'NBD_CMD_INFLIGHT' flag if request is not completed
  nbd: fix race between nbd_alloc_config() and module removal
  nbd: call genl_unregister_family() first in nbd_cleanup()
  md: bcache: check the return value of kzalloc() in detached_dev_do_request()
  bcache: memset on stack variables in bch_btree_check() and bch_sectors_dirty_init()
  block, loop: support partitions without scanning
  bcache: avoid journal no-space deadlock by reserving 1 journal bucket
  bcache: remove incremental dirty sector counting for bch_sectors_dirty_init()
  bcache: improve multithreaded bch_sectors_dirty_init()
  bcache: improve multithreaded bch_btree_check()
  md: fix double free of io_acct_set bioset
  md: Don't set mddev private to NULL in raid0 pers->free
  ...
block, loop: support partitions without scanning 2022-05-27T12:39:00+00:00 Christoph Hellwig hch@lst.de 2022-05-27T05:58:06+00:00 b9684a71fca793213378dd410cd11675d973eaa1 Historically we did distinguish between a flag that surpressed partition scanning, and a combinations of the minors variable and another flag if any partitions were supported. This was generally confusing and doesn't make much sense, but some corner case uses of the loop driver actually do want to support manually added partitions on a device that does not actively scan for partitions. To make things worsee the loop driver also wants to dynamically toggle the scanning for partitions on a live gendisk, which makes the disk->flags updates non-atomic. Introduce a new GD_SUPPRESS_PART_SCAN bit in disk->state that disables just scanning for partitions, and toggle that instead of GENHD_FL_NO_PART in the loop driver. Fixes: 1ebe2e5f9d68 ("block: remove GENHD_FL_EXT_DEVT") Reported-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20220527055806.1972352-1-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk> 
Historically we did distinguish between a flag that surpressed partition
scanning, and a combinations of the minors variable and another flag if
any partitions were supported.  This was generally confusing and doesn't
make much sense, but some corner case uses of the loop driver actually
do want to support manually added partitions on a device that does not
actively scan for partitions.  To make things worsee the loop driver
also wants to dynamically toggle the scanning for partitions on a live
gendisk, which makes the disk->flags updates non-atomic.

Introduce a new GD_SUPPRESS_PART_SCAN bit in disk->state that disables
just scanning for partitions, and toggle that instead of GENHD_FL_NO_PART
in the loop driver.

Fixes: 1ebe2e5f9d68 ("block: remove GENHD_FL_EXT_DEVT")
Reported-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220527055806.1972352-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>