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Coly Li b35fd7422c block: check queue's limits.discard_granularity in __blkdev_issue_discard()
If create a loop device with a backing NVMe SSD, current loop device
driver doesn't correctly set its  queue's limits.discard_granularity and
leaves it as 0. If a discard request at LBA 0 on this loop device, in
__blkdev_issue_discard() the calculated req_sects will be 0, and a zero
length discard request will trigger a BUG() panic in generic block layer
code at block/blk-mq.c:563.

[  955.565006][   C39] ------------[ cut here ]------------
[  955.559660][   C39] invalid opcode: 0000 [] SMP NOPTI
[  955.622171][   C39] CPU: 39 PID: 248 Comm: ksoftirqd/39 Tainted: G            E     5.8.0-default+ 
[  955.622171][   C39] Hardware name: Lenovo ThinkSystem SR650 -[7X05CTO1WW]-/-[7X05CTO1WW]-, BIOS -[IVE160M-2.70]- 07/17/2020
[  955.622175][   C39] RIP: 0010:blk_mq_end_request+0x107/0x110
[  955.622177][   C39] Code: 48 8b 03 e9 59 ff ff ff 48 89 df 5b 5d 41 5c e9 9f ed ff ff 48 8b 35 98 3c f4 00 48 83 c7 10 48 83 c6 19 e8 cb 56 c9 ff eb cb <0f> 0b 0f 1f 80 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 56 41 54
[  955.622179][   C39] RSP: 0018:ffffb1288701fe28 EFLAGS: 00010202
[  955.749277][   C39] RAX: 0000000000000001 RBX: ffff956fffba5080 RCX: 0000000000004003
[  955.749278][   C39] RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000000
[  955.749279][   C39] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
[  955.749279][   C39] R10: ffffb1288701fd28 R11: 0000000000000001 R12: ffffffffa8e05160
[  955.749280][   C39] R13: 0000000000000004 R14: 0000000000000004 R15: ffffffffa7ad3a1e
[  955.749281][   C39] FS:  0000000000000000(0000) GS:ffff95bfbda00000(0000) knlGS:0000000000000000
[  955.749282][   C39] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  955.749282][   C39] CR2: 00007f6f0ef766a8 CR3: 0000005a37012002 CR4: 00000000007606e0
[  955.749283][   C39] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  955.749284][   C39] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  955.749284][   C39] PKRU: 55555554
[  955.749285][   C39] Call Trace:
[  955.749290][   C39]  blk_done_softirq+0x99/0xc0
[  957.550669][   C39]  __do_softirq+0xd3/0x45f
[  957.550677][   C39]  ? smpboot_thread_fn+0x2f/0x1e0
[  957.550679][   C39]  ? smpboot_thread_fn+0x74/0x1e0
[  957.550680][   C39]  ? smpboot_thread_fn+0x14e/0x1e0
[  957.550684][   C39]  run_ksoftirqd+0x30/0x60
[  957.550687][   C39]  smpboot_thread_fn+0x149/0x1e0
[  957.886225][   C39]  ? sort_range+0x20/0x20
[  957.886226][   C39]  kthread+0x137/0x160
[  957.886228][   C39]  ? kthread_park+0x90/0x90
[  957.886231][   C39]  ret_from_fork+0x22/0x30
[  959.117120][   C39] ---[ end trace 3dacdac97e2ed164 ]---

This is the procedure to reproduce the panic,
  # modprobe scsi_debug delay=0 dev_size_mb=2048 max_queue=1
  # losetup -f /dev/nvme0n1 --direct-io=on
  # blkdiscard /dev/loop0 -o 0 -l 0x200

This patch fixes the issue by checking q->limits.discard_granularity in
__blkdev_issue_discard() before composing the discard bio. If the value
is 0, then prints a warning oops information and returns -EOPNOTSUPP to
the caller to indicate that this buggy device driver doesn't support
discard request.

Fixes: 9b15d109a6 ("block: improve discard bio alignment in __blkdev_issue_discard()")
Fixes: c52abf5630 ("loop: Better discard support for block devices")
Reported-and-suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Enzo Matsumiya <ematsumiya@suse.com>
Cc: Evan Green <evgreen@chromium.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Xiao Ni <xni@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-08-05 17:15:47 -06:00
Documentation MMC core: 2020-08-05 13:23:24 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch hmm related patches for 5.9 2020-08-05 13:28:50 -07:00
block block: check queue's limits.discard_granularity in __blkdev_issue_discard() 2020-08-05 17:15:47 -06:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto It's been a busy cycle for documentation - hopefully the busiest for a 2020-08-04 22:47:54 -07:00
drivers hmm related patches for 5.9 2020-08-05 13:28:50 -07:00
fs Driver core changes for 5.9-rc1 2020-08-05 11:52:17 -07:00
include hmm related patches for 5.9 2020-08-05 13:28:50 -07:00
init It's been a busy cycle for documentation - hopefully the busiest for a 2020-08-04 22:47:54 -07:00
ipc mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
kernel Driver core changes for 5.9-rc1 2020-08-05 11:52:17 -07:00
lib hmm related patches for 5.9 2020-08-05 13:28:50 -07:00
mm hmm related patches for 5.9 2020-08-05 13:28:50 -07:00
net It's been a busy cycle for documentation - hopefully the busiest for a 2020-08-04 22:47:54 -07:00
samples It's been a busy cycle for documentation - hopefully the busiest for a 2020-08-04 22:47:54 -07:00
scripts Driver core changes for 5.9-rc1 2020-08-05 11:52:17 -07:00
security cap-checkpoint-restore-v5.9 2020-08-04 15:02:07 -07:00
sound Remove uninitialized_var() macro for v5.9-rc1 2020-08-04 13:49:43 -07:00
tools hmm related patches for 5.9 2020-08-05 13:28:50 -07:00
usr usr: Add support for zstd compressed initramfs 2020-07-31 11:49:08 +02:00
virt entry: Provide infrastructure for work before transitioning to guest mode 2020-07-24 15:03:42 +02:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: Add ZSTD-compressed files 2020-07-31 11:50:49 +02:00
.mailmap It's been a busy cycle for documentation - hopefully the busiest for a 2020-08-04 22:47:54 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Replace HTTP links with HTTPS ones 2020-07-23 14:53:58 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MMC core: 2020-08-05 13:23:24 -07:00
Makefile Automatic variable initialization updates for v5.9-rc1 2020-08-04 13:38:35 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.