The lock around counting the channel queue length in the BIODASDINFO
ioctl was incorrectly changed to the dasd_block->queue_lock with commit
583d6535 ("dasd: remove dead code"). This can lead to endless list
iterations and a subsequent crash.

The queue_lock is supposed to be used only for queue lists belonging to
dasd_block. For dasd_device related queue lists the ccwdev lock must be
used.

Fix the mentioned issues by correctly using the ccwdev lock instead of
the queue lock.

Fixes: 583d6535

 ("dasd: remove dead code")
Cc: stable@vger.kernel.org # v5.0+
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://lore.kernel.org/r/20230609153750.1258763-2-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Memory/pages are not freed, when unloading nullblk driver.

Steps to reproduce issue
  1.free -h
        total        used        free      shared  buff/cache   available
Mem:    7.8Gi       260Mi       7.1Gi       3.0Mi       395Mi       7.3Gi
Swap:      0B          0B          0B
  2.modprobe null_blk memory_backed=1
  3.dd if=/dev/urandom of=/dev/nullb0 oflag=direct bs=1M count=1000
  4.modprobe -r null_blk
  5.free -h
        total        used        free      shared  buff/cache   available
Mem:    7.8Gi       1.2Gi       6.1Gi       3.0Mi       398Mi       6.3Gi
Swap:      0B          0B          0B

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Link: https://lore.kernel.org/r/20230605062354.24785-1-nj.shetty@samsung.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The nr_active counter continues to increase over time which causes the
blk_mq_get_tag to hang until the thread is rescheduled to a different
core despite there are still tags available.

kernel-stack

  INFO: task inboundIOReacto:3014879 blocked for more than 2 seconds
  Not tainted 6.1.15-amd64 #1 Debian 6.1.15~debian11
  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  task:inboundIOReacto state:D stack:0  pid:3014879 ppid:4557 flags:0x00000000
    Call Trace:
    <TASK>
    __schedule+0x351/0xa20
    scheduler+0x5d/0xe0
    io_schedule+0x42/0x70
    blk_mq_get_tag+0x11a/0x2a0
    ? dequeue_task_stop+0x70/0x70
    __blk_mq_alloc_requests+0x191/0x2e0

kprobe output showing RQF_MQ_INFLIGHT bit is not cleared before
__blk_mq_free_request being called.

  320    320  kworker/29:1H __blk_mq_free_request rq_flags 0x220c0 in-flight 1
         b'__blk_mq_free_request+0x1 [kernel]'
         b'bt_iter+0x50 [kernel]'
         b'blk_mq_queue_tag_busy_iter+0x318 [kernel]'
         b'blk_mq_timeout_work+0x7c [kernel]'
         b'process_one_work+0x1c4 [kernel]'
         b'worker_thread+0x4d [kernel]'
         b'kthread+0xe6 [kernel]'
         b'ret_from_fork+0x1f [kernel]'

Signed-off-by: Tian Lan <tian.lan@twosigma.com>
Fixes: 2e315dc0

 ("blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230513221227.497327-1-tilan7663@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull NVMe fixes from Keith:

"nvme fixes for Linux 6.4

 - Fixes for spurious Keep Alive timeouts (Uday)
 - Fix for command type check on passthrough actions (Min)
 - Fix for nvme command name for error logging (Christoph)"

* tag 'nvme-6.4-2023-06-01' of git://git.infradead.org/nvme:
  nvme: fix the name of Zone Append for verbose logging
  nvme: improve handling of long keep alives
  nvme: check IO start time when deciding to defer KA
  nvme: double KA polling frequency to avoid KATO with TBKAS on
  nvme: fix miss command type check

No Management involved in Zone Appened.

Fixes: bd83fe6f

 ("nvme: add verbose error logging")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alan Adamson <alan.adamson@oracle.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

Upon keep alive completion, nvme_keep_alive_work is scheduled with the
same delay every time. If keep alive commands are completing slowly,
this may cause a keep alive timeout. The following trace illustrates the
issue, taking KATO = 8 and TBKAS off for simplicity:

1. t = 0: run nvme_keep_alive_work, send keep alive
2. t = ε: keep alive reaches controller, controller restarts its keep
          alive timer
3. t = 4: host receives keep alive completion, schedules
          nvme_keep_alive_work with delay 4
4. t = 8: run nvme_keep_alive_work, send keep alive

Here, a keep alive having RTT of 4 causes a delay of at least 8 - ε
between the controller receiving successive keep alives. With ε small,
the controller is likely to detect a keep alive timeout.

Fix this by calculating the RTT of the keep alive command, and adjusting
the scheduling delay of the next keep alive work accordingly.

Reported-by: Costa Sapuntzakis <costa@purestorage.com>
Reported-by: Randy Jennings <randyj@purestorage.com>
Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

When a command completes, we set a flag which will skip sending a
keep alive at the next run of nvme_keep_alive_work when TBKAS is on.
However, if the command was submitted long ago, it's possible that
the controller may have also restarted its keep alive timer (as a
result of receiving the command) long ago. The following trace
demonstrates the issue, assuming TBKAS is on and KATO = 8 for
simplicity:

1. t = 0: submit I/O commands A, B, C, D, E
2. t = 0.5: commands A, B, C, D, E reach controller, restart its keep
            alive timer
3. t = 1: A completes
4. t = 2: run nvme_keep_alive_work, see recent completion, do nothing
5. t = 3: B completes
6. t = 4: run nvme_keep_alive_work, see recent completion, do nothing
7. t = 5: C completes
8. t = 6: run nvme_keep_alive_work, see recent completion, do nothing
9. t = 7: D completes
10. t = 8: run nvme_keep_alive_work, see recent completion, do nothing
11. t = 9: E completes

At this point, 8.5 seconds have passed without restarting the
controller's keep alive timer, so the controller will detect a keep
alive timeout.

Fix this by checking the IO start time when deciding to defer sending a
keep alive command. Only set comp_seen if the command started after the
most recent run of nvme_keep_alive_work. With this change, the
completions of B, C, and D will not set comp_seen and the run of
nvme_keep_alive_work at t = 4 will send a keep alive.

Reported-by: Costa Sapuntzakis <costa@purestorage.com>
Reported-by: Randy Jennings <randyj@purestorage.com>
Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

With TBKAS on, the completion of one command can defer sending a
keep alive for up to twice the delay between successive runs of
nvme_keep_alive_work. The current delay of KATO / 2 thus makes it
possible for one command to defer sending a keep alive for up to
KATO, which can result in the controller detecting a KATO. The following
trace demonstrates the issue, taking KATO = 8 for simplicity:

1. t = 0: run nvme_keep_alive_work, no keep-alive sent
2. t = ε: I/O completion seen, set comp_seen = true
3. t = 4: run nvme_keep_alive_work, see comp_seen == true,
          skip sending keep-alive, set comp_seen = false
4. t = 8: run nvme_keep_alive_work, see comp_seen == false,
          send a keep-alive command.

Here, there is a delay of 8 - ε between receiving a command completion
and sending the next command. With ε small, the controller is likely to
detect a keep alive timeout.

Fix this by running nvme_keep_alive_work with a delay of KATO / 4
whenever TBKAS is on. Going through the above trace now gives us a
worst-case delay of 4 - ε, which is in line with the recommendation of
sending a command every KATO / 2 in the NVMe specification.

Reported-by: Costa Sapuntzakis <costa@purestorage.com>
Reported-by: Randy Jennings <randyj@purestorage.com>
Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

In the function nvme_passthru_end(), only the value of the command
opcode is checked, without checking the command type (IO command or
Admin command). When we send a Dataset Management command (The opcode
of the Dataset Management command is the same as the Set Feature
command), kernel thinks it is a set feature command, then sets the
controller's keep alive interval, and calls nvme_keep_alive_work().

Signed-off-by: min15.li <min15.li@samsung.com>
Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

The scsi driver function sd_read_block_characteristics() always calls
disk_set_zoned() to a disk zoned model correctly, in case the device
model changed. This is done even for regular disks to set the zoned
model to BLK_ZONED_NONE and free any zone related resources if the drive
previously was zoned.

This behavior significantly impact the time it takes to revalidate disks
on a large system as the call to disk_clear_zone_settings() done from
disk_set_zoned() for the BLK_ZONED_NONE case results in the device
request queued to be frozen, even if there are no zone resources to
free.

Avoid this overhead for non-zoned devices by not calling
disk_clear_zone_settings() in disk_set_zoned() if the device model
was already set to BLK_ZONED_NONE, which is always the case for regular
devices.

Reported by: Brian Bunker <brian@purestorage.com>

Fixes: 508aebb8

 ("block: introduce blk_queue_clear_zone_settings()")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230529073237.1339862-1-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Merge tag 'md-fixes-2023-05-24' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md into block-6.4

Pull MD fix from Song:

"This change fixes a raid5 regression since 5.12 kernels."

* tag 'md-fixes-2023-05-24' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md/raid5: fix miscalculation of 'end_sector' in raid5_read_one_chunk()

Pull NVMe fix from Keith:

"nvme fixes for 6.4

 One nvme quirk (Tatsuki)"

* tag 'nvme-6.4-2023-05-26' of git://git.infradead.org/nvme:
  NVMe: Add MAXIO 1602 to bogus nid list.

HIKSEMI FUTURE M.2 SSD uses the same dummy nguid and eui64.
I confirmed it with my two devices.

This patch marks the controller as NVME_QUIRK_BOGUS_NID.

---------------------------------------------------------
sugi@tempest:~% sudo nvme id-ctrl /dev/nvme0
NVME Identify Controller:
vid       : 0x1e4b
ssvid     : 0x1e4b
sn        : 30096022612
mn        : HS-SSD-FUTURE 2048G
fr        : SN10542
rab       : 0
ieee      : 000000
cmic      : 0
mdts      : 7
cntlid    : 0
ver       : 0x10400
rtd3r     : 0x7a120
rtd3e     : 0x1e8480
oaes      : 0x200
ctratt    : 0x2
rrls      : 0
cntrltype : 1
fguid     : 00000000-0000-0000-0000-000000000000
<snip...>
---------------------------------------------------------

---------------------------------------------------------
sugi@tempest:~% sudo nvme id-ns /dev/nvme0n1
NVME Identify Namespace 1:
<snip...>
nguid   : 00000000000000000000000000000000
eui64   : 0000000000000002
lbaf  0 : ms:0   lbads:9  rp:0 (in use)
---------------------------------------------------------

Signed-off-by: Tatsuki Sugiura <sugi@nemui.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

'end_sector' is compared to 'rdev->recovery_offset', which is offset to
rdev, however, commit e82ed3a4 ("md/raid6: refactor
raid5_read_one_chunk") changes the calculation of 'end_sector' to offset
to the array. Fix this miscalculation.

Fixes: e82ed3a4

 ("md/raid6: refactor raid5_read_one_chunk")
Cc: stable@vger.kernel.org # v5.12+
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230524014118.3172781-1-yukuai1@huaweicloud.com

Since the dawn of time bio_check_eod has a check for a non-zero size of
the device.  This doesn't really make any sense as we never want to send
I/O to a device that's been set to zero size, or never moved out of that.

I am a bit surprised we haven't caught this for a long time, but the
removal of the extra validation inside of zram caused syzbot to trip
over this issue recently.  I've added a Fixes tag for that commit, but
the issue really goes back way before git history.

Fixes: 9fe95bab

 ("zram: remove valid_io_request")
Reported-by:  <syzbot+b8d61a58b7c7ebd2c8e0@syzkaller.appspotmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230524060538.1593686-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

commit <8af870aa> ("block: enable bio caching use for passthru IO")
introduced bio-cache for passthru IO. In case when nr_vecs are greater
than BIO_INLINE_VECS, bio and bvecs are allocated from mempool (instead
of percpu cache) and REQ_ALLOC_CACHE is cleared. This causes the side
effect of not freeing bio/bvecs into mempool on completion.

This patch lets the passthru IO fallback to allocation using bio_kmalloc
when nr_vecs are greater than BIO_INLINE_VECS. The corresponding bio
is freed during call to blk_mq_map_bio_put during completion.

Cc: stable@vger.kernel.org # 6.1
fixes <8af870aa

> ("block: enable bio caching use for passthru IO")

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Link: https://lore.kernel.org/r/20230523111709.145676-1-anuj20.g@samsung.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Current email address of Paolo Valente is no longer valid, use a good one.

Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Link: https://lore.kernel.org/r/20230523091724.26636-1-paolo.valente@unimore.it
Signed-off-by: Jens Axboe <axboe@kernel.dk>

If multiple CPUs are sharing the same hardware queue, it can
cause leak in the active queue counter tracking when __blk_mq_tag_busy()
is executed simultaneously.

Fixes: ee78ec10

 ("blk-mq: blk_mq_tag_busy is no need to return a value")
Signed-off-by: Tian Lan <tian.lan@twosigma.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20230522210555.794134-1-tilan7663@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

commit b11d31ae ("blk-wbt: remove unnecessary check in
wbt_enable_default()") removes the checking of CONFIG_BLK_WBT_MQ by
mistake, which is used to control enable or disable wbt by default.

Fix the problem by adding back the checking. This patch also do a litter
cleanup to make related code more readable.

Fixes: b11d31ae

 ("blk-wbt: remove unnecessary check in wbt_enable_default()")
Reported-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/lkml/CAKXUXMzfKq_J9nKHGyr5P5rvUETY4B-fxoQD4sO+NYjFOfVtZA@mail.gmail.com/t/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230522121854.2928880-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The NFL4_UFLG_MASK define slipped in in commit 9208d414


("block: add a ->get_unique_id method") and should never have been
added, as NFSD as the only user of it already has it's copy.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230520090010.527046-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

User should not be able to write block device if it is read-only at
block level (e.g force_ro attribute). This is ensured in the regular
fops write operation (blkdev_write_iter) but not when writing via
user mapping (mmap), allowing user to actually write a read-only
block device via a PROT_WRITE mapping.

Example: This can lead to integrity issue of eMMC boot partition
(e.g mmcblk0boot0) which is read-only by default.

To fix this issue, simply deny shared writable mapping if the block
is readonly.

Note: Block remains writable if switch to read-only is performed
after the initial mapping, but this is expected behavior according
to commit a32e236e

 ("Partially revert "block: fail op_is_write()
requests to read-only partitions"")'.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230510074223.991297-1-loic.poulain@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Formatting a thin-provisioned (ESE) device that is part of a PPRC copy
relation might fail with the following error:

dasd-eckd 0.0.f500: An error occurred in the DASD device driver, reason=09
[...]
24 Byte: 0 MSG 4, no MSGb to SYSOP

During format of an ESE disk the Release Allocated Space command is used.
A bit in the payload of the command is set that is not allowed to be set
for devices in a copy relation. This bit is set to allow the partial
release of an extent.

Check for the existence of a copy relation before setting the respective
bit.

Fixes: 91dc4a19

 ("s390/dasd: Add new ioctl to release space")
Cc: stable@kernel.org # 5.3+
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Link: https://lore.kernel.org/r/20230519102340.3854819-2-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull NVMe fixes from Keith:

"nvme fixes for Linux 6.4

 - More device quirks (Sagi, Hristo, Adrian, Daniel)
 - Controller delete race (Maurizo)
 - Multipath cleanup fix (Christoph)"

* tag 'nvme-6.4-2023-05-18' of git://git.infradead.org/nvme:
  nvme-pci: Add quirk for Teamgroup MP33 SSD
  nvme: do not let the user delete a ctrl before a complete initialization
  nvme-multipath: don't call blk_mark_disk_dead in nvme_mpath_remove_disk
  nvme-pci: clamp max_hw_sectors based on DMA optimized limitation
  nvme-pci: add quirk for missing secondary temperature thresholds
  nvme-pci: add NVME_QUIRK_BOGUS_NID for HS-SSD-FUTURE 2048G

Add a quirk for Teamgroup MP33 that reports duplicate ids for disk.

Signed-off-by: Daniel Smith <dansmith@ds.gy>
[kch: patch formatting]
Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Tested-by: Daniel Smith <dansmith@ds.gy>
Signed-off-by: Keith Busch <kbusch@kernel.org>

When handling UBLK_IO_FETCH_REQ, ctx->uring_lock is grabbed first, then
ub->mutex is acquired.

When handling UBLK_CMD_STOP_DEV or UBLK_CMD_DEL_DEV, ub->mutex is
grabbed first, then calling io_uring_cmd_done() for canceling uring
command, in which ctx->uring_lock may be required.

Real deadlock only happens when all the above commands are issued from
same uring context, and in reality different uring contexts are often used
for handing control command and IO command.

Fix the issue by using io_uring_cmd_complete_in_task() to cancel command
in ublk_cancel_dev(ublk_cancel_queue).

Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Closes: https://lore.kernel.org/linux-block/becol2g7sawl4rsjq2dztsbc7mqypfqko6wzsyoyazqydoasml@rcxarzwidrhk
Cc: Ziyang Zhang <ZiyangZhang@linux.alibaba.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Link: https://lore.kernel.org/r/20230517133408.210944-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

If a userspace application performes a "delete_controller" command
early during the ctrl initialization, the delete operation
may race against the init code and the kernel will crash.

nvme nvme5: Connect command failed: host path error
nvme nvme5: failed to connect queue: 0 ret=880
PF: supervisor write access in kernel mode
PF: error_code(0x0002) - not-present page
 blk_mq_quiesce_queue+0x18/0x90
 nvme_tcp_delete_ctrl+0x24/0x40 [nvme_tcp]
 nvme_do_delete_ctrl+0x7f/0x8b [nvme_core]
 nvme_sysfs_delete.cold+0x8/0xd [nvme_core]
 kernfs_fop_write_iter+0x124/0x1b0
 new_sync_write+0xff/0x190
 vfs_write+0x1ef/0x280

Fix the crash by checking the NVME_CTRL_STARTED_ONCE bit;
if it's not set it means that the nvme controller is still
in the process of getting initialized and the kernel
will return an -EBUSY error to userspace.
Set the NVME_CTRL_STARTED_ONCE later in the nvme_start_ctrl()
function, after the controller start operation is completed.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

nvme_mpath_remove_disk is called after del_gendisk, at which point a
blk_mark_disk_dead call doesn't make any sense.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>

Documentation/block/request.rst is outdated and should be removed.
Also delete its entry in the block/index.rst file.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Link: https://lore.kernel.org/r/20230507182606.12647-1-rdunlap@infradead.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

In case of CONFIG_BLKDEV_UBLK_LEGACY_OPCODES, type of cmd opcode could
be 0 or 'u'; and type can only be 'u' if CONFIG_BLKDEV_UBLK_LEGACY_OPCODES
isn't set.

So fix the wrong check.

Fixes: 2d786e66

 ("block: ublk: switch to ioctl command encoding")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230505153142.1258336-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Since flush bios are implemented as writes with no data and
the preflush flag per Christoph's comment [1].

And we need to change it in rnbd accordingly. Otherwise, I
got splatting when create fs from rnbd client.

[  464.028545] ------------[ cut here ]------------
[  464.028553] WARNING: CPU: 0 PID: 65 at block/blk-core.c:751 submit_bio_noacct+0x32c/0x5d0
[ ... ]
[  464.028668] CPU: 0 PID: 65 Comm: kworker/0:1H Tainted: G           OE      6.4.0-rc1 #9
[  464.028671] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.15.0-0-g2dd4b9b-rebuilt.opensuse.org 04/01/2014
[  464.028673] Workqueue: ib-comp-wq ib_cq_poll_work [ib_core]
[  464.028717] RIP: 0010:submit_bio_noacct+0x32c/0x5d0
[  464.028720] Code: 03 0f 85 51 fe ff ff 48 8b 43 18 8b 88 04 03 00 00 85 c9 0f 85 3f fe ff ff e9 be fd ff ff 0f b6 d0 3c 0d 74 26 83 fa 01 74 21 <0f> 0b b8 0a 00 00 00 e9 56 fd ff ff 4c 89 e7 e8 70 a1 03 00 84 c0
[  464.028722] RSP: 0018:ffffaf3680b57c68 EFLAGS: 00010202
[  464.028724] RAX: 0000000000060802 RBX: ffffa09dcc18bf00 RCX: 0000000000000000
[  464.028726] RDX: 0000000000000002 RSI: 0000000000000000 RDI: ffffa09dde081d00
[  464.028727] RBP: ffffaf3680b57c98 R08: ffffa09dde081d00 R09: ffffa09e38327200
[  464.028729] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa09dde081d00
[  464.028730] R13: ffffa09dcb06e1e8 R14: 0000000000000000 R15: 0000000000200000
[  464.028733] FS:  0000000000000000(0000) GS:ffffa09e3bc00000(0000) knlGS:0000000000000000
[  464.028735] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  464.028736] CR2: 000055a4e8206c40 CR3: 0000000119f06000 CR4: 00000000003506f0
[  464.028738] Call Trace:
[  464.028740]  <TASK>
[  464.028746]  submit_bio+0x1b/0x80
[  464.028748]  rnbd_srv_rdma_ev+0x50d/0x10c0 [rnbd_server]
[  464.028754]  ? percpu_ref_get_many.constprop.0+0x55/0x140 [rtrs_server]
[  464.028760]  ? __this_cpu_preempt_check+0x13/0x20
[  464.028769]  process_io_req+0x1dc/0x450 [rtrs_server]
[  464.028775]  rtrs_srv_inv_rkey_done+0x67/0xb0 [rtrs_server]
[  464.028780]  __ib_process_cq+0xbc/0x1f0 [ib_core]
[  464.028793]  ib_cq_poll_work+0x2b/0xa0 [ib_core]
[  464.028804]  process_one_work+0x2a9/0x580

[1]. https://lore.kernel.org/all/ZFHgefWofVt24tRl@infradead.org/

Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20230512034631.28686-1-guoqing.jiang@linux.dev
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The debugfs_create_dir function returns ERR_PTR in case of error, and the
only correct way to check if an error occurred is 'IS_ERR' inline function.
This patch will replace the null-comparison with IS_ERR.

Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Link: https://lore.kernel.org/r/20230512130533.98709-1-ivan.orlov0322@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Merge tag 'perf-tools-for-v6.4-3-2023-05-06' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux

Pull perf tool updates from Arnaldo Carvalho de Melo:
 "Third version of perf tool updates, with the build problems with with
  using a 'vmlinux.h' generated from the main build fixed, and the bpf
  skeleton build disabled by default.

  Build:

   - Require libtraceevent to build, one can disable it using
     NO_LIBTRACEEVENT=1.

     It is required for tools like 'perf sched', 'perf kvm', 'perf
     trace', etc.

     libtraceevent is available in most distros so installing
     'libtraceevent-devel' should be a one-time event to continue
     building perf as usual.

     Using NO_LIBTRACEEVENT=1 produces tooling that is functional and
     sufficient for lots of users not interested in those libtraceevent
     dependent features.

   - Allow Python support in 'perf script' when libtraceevent isn't
     linked, as not all features requires it, for instance Intel PT does
     not use tracepoints.

   - Error if the python interpreter needed for jevents to work isn't
     available and NO_JEVENTS=1 isn't set, preventing a build without
     support for JSON vendor events, which is a rare but possible
     condition. The two check error messages:

        $(error ERROR: No python interpreter needed for jevents generation. Install python or build with NO_JEVENTS=1.)
        $(error ERROR: Python interpreter needed for jevents generation too old (older than 3.6). Install a newer python or build with NO_JEVENTS=1.)

   - Make libbpf 1.0 the minimum required when building with out of
     tree, distro provided libbpf.

   - Use libsdtc++'s and LLVM's libcxx's __cxa_demangle, a portable C++
     demangler, add 'perf test' entry for it.

   - Make binutils libraries opt in, as distros disable building with it
     due to licensing, they were used for C++ demangling, for instance.

   - Switch libpfm4 to opt-out rather than opt-in, if libpfm-devel (or
     equivalent) isn't installed, we'll just have a build warning:

       Makefile.config:1144: libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev

   - Add a feature test for scandirat(), that is not implemented so far
     in musl and uclibc, disabling features that need it, such as
     scanning for tracepoints in /sys/kernel/tracing/events.

  perf BPF filters:

   - New feature where BPF can be used to filter samples, for instance:

      $ sudo ./perf record -e cycles --filter 'period > 1000' true
      $ sudo ./perf script
           perf-exec 2273949 546850.708501:       5029 cycles:  ffffffff826f9e25 finish_wait+0x5 ([kernel.kallsyms])
           perf-exec 2273949 546850.708508:      32409 cycles:  ffffffff826f9e25 finish_wait+0x5 ([kernel.kallsyms])
           perf-exec 2273949 546850.708526:     143369 cycles:  ffffffff82b4cdbf xas_start+0x5f ([kernel.kallsyms])
           perf-exec 2273949 546850.708600:     372650 cycles:  ffffffff8286b8f7 __pagevec_lru_add+0x117 ([kernel.kallsyms])
           perf-exec 2273949 546850.708791:     482953 cycles:  ffffffff829190de __mod_memcg_lruvec_state+0x4e ([kernel.kallsyms])
                true 2273949 546850.709036:     501985 cycles:  ffffffff828add7c tlb_gather_mmu+0x4c ([kernel.kallsyms])
                true 2273949 546850.709292:     503065 cycles:      7f2446d97c03 _dl_map_object_deps+0x973 (/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2)

   - In addition to 'period' (PERF_SAMPLE_PERIOD), the other
     PERF_SAMPLE_ can be used for filtering, and also some other sample
     accessible values, from tools/perf/Documentation/perf-record.txt:

        Essentially the BPF filter expression is:

        <term> <operator> <value> (("," | "||") <term> <operator> <value>)*

     The <term> can be one of:
        ip, id, tid, pid, cpu, time, addr, period, txn, weight, phys_addr,
        code_pgsz, data_pgsz, weight1, weight2, weight3, ins_lat, retire_lat,
        p_stage_cyc, mem_op, mem_lvl, mem_snoop, mem_remote, mem_lock,
        mem_dtlb, mem_blk, mem_hops

     The <operator> can be one of:
        ==, !=, >, >=, <, <=, &

     The <value> can be one of:
        <number> (for any term)
        na, load, store, pfetch, exec (for mem_op)
        l1, l2, l3, l4, cxl, io, any_cache, lfb, ram, pmem (for mem_lvl)
        na, none, hit, miss, hitm, fwd, peer (for mem_snoop)
        remote (for mem_remote)
        na, locked (for mem_locked)
        na, l1_hit, l1_miss, l2_hit, l2_miss, any_hit, any_miss, walk, fault (for mem_dtlb)
        na, by_data, by_addr (for mem_blk)
        hops0, hops1, hops2, hops3 (for mem_hops)

  perf lock contention:

   - Show lock type with address.

   - Track and show mmap_lock, siglock and per-cpu rq_lock with address.
     This is done for mmap_lock by following the current->mm pointer:

      $ sudo ./perf lock con -abl -- sleep 10
       contended   total wait     max wait     avg wait            address   symbol
       ...
           16344    312.30 ms      2.22 ms     19.11 us   ffff8cc702595640
           17686    310.08 ms      1.49 ms     17.53 us   ffff8cc7025952c0
               3     84.14 ms     45.79 ms     28.05 ms   ffff8cc78114c478   mmap_lock
            3557     76.80 ms     68.75 us     21.59 us   ffff8cc77ca3af58
               1     68.27 ms     68.27 ms     68.27 ms   ffff8cda745dfd70
               9     54.53 ms      7.96 ms      6.06 ms   ffff8cc7642a48b8   mmap_lock
           14629     44.01 ms     60.00 us      3.01 us   ffff8cc7625f9ca0
            3481     42.63 ms    140.71 us     12.24 us   ffffffff937906ac   vmap_area_lock
           16194     38.73 ms     42.15 us      2.39 us   ffff8cd397cbc560
              11     38.44 ms     10.39 ms      3.49 ms   ffff8ccd6d12fbb8   mmap_lock
               1      5.43 ms      5.43 ms      5.43 ms   ffff8cd70018f0d8
            1674      5.38 ms    422.93 us      3.21 us   ffffffff92e06080   tasklist_lock
             581      4.51 ms    130.68 us      7.75 us   ffff8cc9b1259058
               5      3.52 ms      1.27 ms    703.23 us   ffff8cc754510070
             112      3.47 ms     56.47 us     31.02 us   ffff8ccee38b3120
             381      3.31 ms     73.44 us      8.69 us   ffffffff93790690   purge_vmap_area_lock
             255      3.19 ms     36.35 us     12.49 us   ffff8d053ce30c80

   - Update default map size to 16384.

   - Allocate single letter option -M for --map-nr-entries, as it is
     proving being frequently used.

   - Fix struct rq lock access for older kernels with BPF's CO-RE
     (Compile once, run everywhere).

   - Fix problems found with MSAn.

  perf report/top:

   - Add inline information when using --call-graph=fp or lbr, as was
     already done to the --call-graph=dwarf callchain mode.

   - Improve the 'srcfile' sort key performance by really using an
     optimization introduced in 6.2 for the 'srcline' sort key that
     avoids calling addr2line for comparision with each sample.

  perf sched:

   - Make 'perf sched latency/map/replay' to use "sched:sched_waking"
     instead of "sched:sched_waking", consistent with 'perf record'
     since d566a9c2 ("perf sched: Prefer sched_waking event when it
     exists").

  perf ftrace:

   - Make system wide the default target for latency subcommand, run the
     following command then generate some network traffic and press
     control+C:

       # perf ftrace latency -T __kfree_skb
     ^C
         DURATION     |      COUNT | GRAPH                                          |
          0 - 1    us |         27 | #############                                  |
          1 - 2    us |         22 | ###########                                    |
          2 - 4    us |          8 | ####                                           |
          4 - 8    us |          5 | ##                                             |
          8 - 16   us |         24 | ############                                   |
         16 - 32   us |          2 | #                                              |
         32 - 64   us |          1 |                                                |
         64 - 128  us |          0 |                                                |
        128 - 256  us |          0 |                                                |
        256 - 512  us |          0 |                                                |
        512 - 1024 us |          0 |                                                |
          1 - 2    ms |          0 |                                                |
          2 - 4    ms |          0 |                                                |
          4 - 8    ms |          0 |                                                |
          8 - 16   ms |          0 |                                                |
         16 - 32   ms |          0 |                                                |
         32 - 64   ms |          0 |                                                |
         64 - 128  ms |          0 |                                                |
        128 - 256  ms |          0 |                                                |
        256 - 512  ms |          0 |                                                |
        512 - 1024 ms |          0 |                                                |
          1 - ...   s |          0 |                                                |
       #

  perf top:

   - Add --branch-history (LBR: Last Branch Record) option, just like
     already available for 'perf record'.

   - Fix segfault in thread__comm_len() where thread->comm was being
     used outside thread->comm_lock.

  perf annotate:

   - Allow configuring objdump and addr2line in ~/.perfconfig., so that
     you can use alternative binaries, such as llvm's.

  perf kvm:

   - Add TUI mode for 'perf kvm stat report'.

  Reference counting:

   - Add reference count checking infrastructure to check for use after
     free, done to the 'cpumap', 'namespaces', 'maps' and 'map' structs,
     more to come.

     To build with it use -DREFCNT_CHECKING=1 in the make command line
     to build tools/perf. Documented at:

       https://perf.wiki.kernel.org/index.php/Reference_Count_Checking

   - The above caught, for instance, fix, present in this series:

        - Fix maps use after put in 'perf test "Share thread maps"':

          'maps' is copied from leader, but the leader is put on line 79
          and then 'maps' is used to read the reference count below - so
          a use after put, with the put of maps happening within
          thread__put.

     Fixed by reversing the order of puts so that the leader is put
     last.

   - Also several fixes were made to places where reference counts were
     not being held.

   - Make this one of the tests in 'make -C tools/perf build-test' to
     regularly build test it and to make sure no direct access to the
     reference counted structs are made, doing that via accessors to
     check the validity of the struct pointer.

  ARM64:

   - Fix 'perf report' segfault when filtering coresight traces by
     sparse lists of CPUs.

   - Add support for 'simd' as a sort field for 'perf report', to show
     ARM's NEON SIMD's predicate flags: "partial" and "empty".

  arm64 vendor events:

   - Add N1 metrics.

  Intel vendor events:

   - Add graniterapids, grandridge and sierraforrest events.

   - Refresh events for: alderlake, aldernaken, broadwell, broadwellde,
     broadwellx, cascadelakx, haswell, haswellx, icelake, icelakex,
     jaketown, meteorlake, knightslanding, sandybridge, sapphirerapids,
     silvermont, skylake, tigerlake and westmereep-dp

   - Refresh metrics for alderlake-n, broadwell, broadwellde,
     broadwellx, haswell, haswellx, icelakex, ivybridge, ivytown and
     skylakex.

  perf stat:

   - Implement --topdown using JSON metrics.

   - Add TopdownL1 JSON metric as a default if present, but disable it
     for now for some Intel hybrid architectures, a series of patches
     addressing this is being reviewed and will be submitted for v6.5.

   - Use metrics for --smi-cost.

   - Update topdown documentation.

  Vendor events (JSON) infrastructure:

   - Add support for computing and printing metric threshold values. For
     instance, here is one found in thesapphirerapids json file:

       {
           "BriefDescription": "Percentage of cycles spent in System Management Interrupts.",
           "MetricExpr": "((msr@aperf@ - cycles) / msr@aperf@ if msr@smi@ > 0 else 0)",
           "MetricGroup": "smi",
           "MetricName": "smi_cycles",
           "MetricThreshold": "smi_cycles > 0.1",
           "ScaleUnit": "100%"
       },

   - Test parsing metric thresholds with the fake PMU in 'perf test
     pmu-events'.

   - Support for printing metric thresholds in 'perf list'.

   - Add --metric-no-threshold option to 'perf stat'.

   - Add rand (reverse and) and has_pmem (optane memory) support to
     metrics.

   - Sort list of input files to avoid depending on the order from
     readdir() helping in obtaining reproducible builds.

  S/390:

   - Add common metrics: - CPI (cycles per instruction), prbstate (ratio
     of instructions executed in problem state compared to total number
     of instructions), l1mp (Level one instruction and data cache misses
     per 100 instructions).

   - Add cache metrics for z13, z14, z15 and z16.

   - Add metric for TLB and cache.

  ARM:

   - Add raw decoding for SPE (Statistical Profiling Extension) v1.3 MTE
     (Memory Tagging Extension) and MOPS (Memory Operations) load/store.

  Intel PT hardware tracing:

   - Add event type names UINTR (User interrupt delivered) and UIRET
     (Exiting from user interrupt routine), documented in table 32-50
     "CFE Packet Type and Vector Fields Details" in the Intel Processor
     Trace chapter of The Intel SDM Volume 3 version 078.

   - Add support for new branch instructions ERETS and ERETU.

   - Fix CYC timestamps after standalone CBR

  ARM CoreSight hardware tracing:

   - Allow user to override timestamp and contextid settings.

   - Fix segfault in dso lookup.

   - Fix timeless decode mode detection.

   - Add separate decode paths for timeless and per-thread modes.

  auxtrace:

   - Fix address filter entire kernel size.

  Miscellaneous:

   - Fix use-after-free and unaligned bugs in the PLT handling routines.

   - Use zfree() to reduce chances of use after free.

   - Add missing 0x prefix for addresses printed in hexadecimal in 'perf
     probe'.

   - Suppress massive unsupported target platform errors in the unwind
     code.

   - Fix return incorrect build_id size in elf_read_build_id().

   - Fix 'perf scripts intel-pt-events.py' IPC output for Python 2 .

   - Add missing new parameter in kfree_skb tracepoint to the python
     scripts using it.

   - Add 'perf bench syscall fork' benchmark.

   - Add support for printing PERF_MEM_LVLNUM_UNC (Uncached access) in
     'perf mem'.

   - Fix wrong size expectation for perf test 'Setup struct
     perf_event_attr' caused by the patch adding
     perf_event_attr::config3.

   - Fix some spelling mistakes"

* tag 'perf-tools-for-v6.4-3-2023-05-06' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux: (365 commits)
  Revert "perf build: Make BUILD_BPF_SKEL default, rename to NO_BPF_SKEL"
  Revert "perf build: Warn for BPF skeletons if endian mismatches"
  perf metrics: Fix SEGV with --for-each-cgroup
  perf bpf skels: Stop using vmlinux.h generated from BTF, use subset of used structs + CO-RE
  perf stat: Separate bperf from bpf_profiler
  perf test record+probe_libc_inet_pton: Fix call chain match on x86_64
  perf test record+probe_libc_inet_pton: Fix call chain match on s390
  perf tracepoint: Fix memory leak in is_valid_tracepoint()
  perf cs-etm: Add fix for coresight trace for any range of CPUs
  perf build: Fix unescaped # in perf build-test
  perf unwind: Suppress massive unsupported target platform errors
  perf script: Add new parameter in kfree_skb tracepoint to the python scripts using it
  perf script: Print raw ip instead of binary offset for callchain
  perf symbols: Fix return incorrect build_id size in elf_read_build_id()
  perf list: Modify the warning message about scandirat(3)
  perf list: Fix memory leaks in print_tracepoint_events()
  perf lock contention: Rework offset calculation with BPF CO-RE
  perf lock contention: Fix struct rq lock access
  perf stat: Disable TopdownL1 on hybrid
  perf stat: Avoid SEGV on counter->name
  ...

Pull debugobjects fix from Thomas Gleixner:
 "A single fix for debugobjects:

  The recent fix to ensure atomicity of lookup and allocation
  inadvertently broke the pool refill mechanism, so that debugobject
  OOMs now in certain situations. The reason is that the functions which
  got updated no longer invoke debug_objecs_init(), which is now the
  only place to care about refilling the tracking object pool.

  Restore the original behaviour by adding explicit refill opportunities
  to those places"

* tag 'core-debugobjects-2023-05-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  debugobject: Ensure pool refill (again)

Pull crypto fixes from Herbert Xu:

 - A long-standing bug in crypto_engine

 - A buggy but harmless check in the sun8i-ss driver

 - A regression in the CRYPTO_USER interface

* tag 'v6.4-p2' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
  crypto: api - Fix CRYPTO_USER checks for report function
  crypto: engine - fix crypto_queue backlog handling
  crypto: sun8i-ss - Fix a test in sun8i_ss_setup_ivs()

Pull cifs fixes from Steve French:
 "smb3 client fixes, mostly DFS or reconnect related:

   - Two DFS connection sharing fixes

   - DFS refresh fix

   - Reconnect fix

   - Two potential use after free fixes

   - Also print prefix patch in mount debug msg

   - Two small cleanup fixes"

* tag '6.4-rc-smb3-client-fixes-part2' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: Remove unneeded semicolon
  cifs: fix sharing of DFS connections
  cifs: avoid potential races when handling multiple dfs tcons
  cifs: protect access of TCP_Server_Info::{origin,leaf}_fullpath
  cifs: fix potential race when tree connecting ipc
  cifs: fix potential use-after-free bugs in TCP_Server_Info::hostname
  cifs: print smb3_fs_context::source when mounting
  cifs: protect session status check in smb2_reconnect()
  SMB3.1.1: correct definition for app_instance_id create contexts

Pull clk fixes from Stephen Boyd:
 "A couple more patches that would be good to get into -rc1:

   - Revert an i.MX patch that's causing video failures because division
     math goes sideways

   - Fix a clang + W=1 build isue where FIELD_PREP() is taking a 32-bit
     variable instead of the usual u64 type

   - Fix a Kconfig bug in the StarFive JH7110 clk config that selects a
     reset controller when it can't be selected"

* tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux:
  clk: starfive: Fix RESET_STARFIVE_JH7110 can't be selected in a specified case
  clk: sp7021: Adjust width of _m in HWM_FIELD_PREP()
  Revert "clk: imx: composite-8m: Add support to determine_rate"

Pull mailbox updates from Jassi Brar:

 - mailbox api: allow direct registration to a channel and convert omap
   and pcc to use mbox_bind_client

 - omap and hi6220 : use of_property_read_bool

 - test: fix double-free and use spinlock header

 - rockchip and bcm-pdc: drop of_match_ptr

 - mpfs: change config symbol

 - mediatek gce: support MT6795

 - qcom apcs: consolidate of_device_id and support IPQ9574

* tag 'mailbox-v6.4' of git://git.linaro.org/landing-teams/working/fujitsu/integration:
  dt-bindings: mailbox: qcom: add compatible for IPQ9574 SoC
  mailbox: qcom-apcs-ipc: do not grow the of_device_id
  dt-bindings: mailbox: qcom,apcs-kpss-global: use fallbacks for few variants
  dt-bindings: mailbox: mediatek,gce-mailbox: Add support for MT6795
  mailbox: mpfs: convert SOC_MICROCHIP_POLARFIRE to ARCH_MICROCHIP_POLARFIRE
  mailbox: bcm-pdc: drop of_match_ptr for ID table
  mailbox: rockchip: drop of_match_ptr for ID table
  mailbox: mailbox-test: Fix potential double-free in mbox_test_message_write()
  mailbox: mailbox-test: Explicitly include header for spinlock support
  mailbox: Use of_property_read_bool() for boolean properties
  mailbox: pcc: Use mbox_bind_client
  mailbox: omap: Use mbox_bind_client
  mailbox: Allow direct registration to a channel

Pull more io_uring updates from Jens Axboe:
 "Nothing major in here, just two different parts:

   - A small series from Breno that enables passing the full SQE down
     for ->uring_cmd().

     This is a prerequisite for enabling full network socket operations.
     Queued up a bit late because of some stylistic concerns that got
     resolved, would be nice to have this in 6.4-rc1 so the dependent
     work will be easier to handle for 6.5.

   - Fix for the huge page coalescing, which was a regression introduced
     in the 6.3 kernel release (Tobias)"

* tag 'for-6.4/io_uring-2023-05-07' of git://git.kernel.dk/linux:
  io_uring: Remove unnecessary BUILD_BUG_ON
  io_uring: Pass whole sqe to commands
  io_uring: Create a helper to return the SQE size
  io_uring/rsrc: check for nonconsecutive pages

This reverts commit a980755b

.

We need to better polish building with BPF skels, so revert back to
making it an experimental feature that has to be explicitely enabled
using BUILD_BPF_SKEL=1.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>