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Li Nan 2d0738a832 md: fix deadlock between mddev_suspend and flush bio 
[ Upstream commit 611d5cbc0b ]

Deadlock occurs when mddev is being suspended while some flush bio is in
progress. It is a complex issue.

T1. the first flush is at the ending stage, it clears 'mddev->flush_bio'
    and tries to submit data, but is blocked because mddev is suspended
    by T4.
T2. the second flush sets 'mddev->flush_bio', and attempts to queue
    md_submit_flush_data(), which is already running (T1) and won't
    execute again if on the same CPU as T1.
T3. the third flush inc active_io and tries to flush, but is blocked because
    'mddev->flush_bio' is not NULL (set by T2).
T4. mddev_suspend() is called and waits for active_io dec to 0 which is inc
    by T3.

  T1		T2		T3		T4
  (flush 1)	(flush 2)	(third 3)	(suspend)
  md_submit_flush_data
   mddev->flush_bio = NULL;
   .
   .	 	md_flush_request
   .	  	 mddev->flush_bio = bio
   .	  	 queue submit_flushes
   .		 .
   .		 .		md_handle_request
   .		 .		 active_io + 1
   .		 .		 md_flush_request
   .		 .		  wait !mddev->flush_bio
   .		 .
   .		 .				mddev_suspend
   .		 .				 wait !active_io
   .		 .
   .		 submit_flushes
   .		 queue_work md_submit_flush_data
   .		 //md_submit_flush_data is already running (T1)
   .
   md_handle_request
    wait resume

The root issue is non-atomic inc/dec of active_io during flush process.
active_io is dec before md_submit_flush_data is queued, and inc soon
after md_submit_flush_data() run.
  md_flush_request
    active_io + 1
    submit_flushes
      active_io - 1
      md_submit_flush_data
        md_handle_request
        active_io + 1
          make_request
        active_io - 1

If active_io is dec after md_handle_request() instead of within
submit_flushes(), make_request() can be called directly intead of
md_handle_request() in md_submit_flush_data(), and active_io will
only inc and dec once in the whole flush process. Deadlock will be
fixed.

Additionally, the only difference between fixing the issue and before is
that there is no return error handling of make_request(). But after
previous patch cleaned md_write_start(), make_requst() only return error
in raid5_make_request() by dm-raid, see commit 41425f96d7 ("dm-raid456,
md/raid456: fix a deadlock for dm-raid456 while io concurrent with
reshape)". Since dm always splits data and flush operation into two
separate io, io size of flush submitted by dm always is 0, make_request()
will not be called in md_submit_flush_data(). To prevent future
modifications from introducing issues, add WARN_ON to ensure
make_request() no error is returned in this context.

Fixes: fa2bbff7b0 ("md: synchronize flush io with array reconfiguration")
Signed-off-by: Li Nan <linan122@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240525185257.3896201-3-linan666@huaweicloud.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-08-03 08:53:20 +02:00
arch powerpc/configs: Update defconfig with now user-visible CONFIG_FSL_IFC 2024-08-03 08:53:19 +02:00
block block/ioctl: prefer different overflow check 2024-06-27 13:49:01 +02:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: aead,cipher - zeroize key buffer after use 2024-07-11 12:49:04 +02:00
Documentation scsi: sr: Fix unintentional arithmetic wraparound 2024-07-25 09:50:40 +02:00
drivers md: fix deadlock between mddev_suspend and flush bio 2024-08-03 08:53:20 +02:00
fs filelock: Fix fcntl/close race recovery compat path 2024-07-27 11:34:10 +02:00
include cachefiles: fix slab-use-after-free in fscache_withdraw_volume() 2024-07-25 09:50:57 +02:00
init smp: Provide 'setup_max_cpus' definition on UP too 2024-06-16 13:47:49 +02:00
io_uring io_uring/rsrc: fix incorrect assignment of iter->nr_segs in io_import_fixed 2024-06-27 13:49:10 +02:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel rcu/tasks: Fix stale task snaphot for Tasks Trace 2024-08-03 08:53:20 +02:00
lib cpumask: limit FORCE_NR_CPUS to just the UP case 2024-07-25 09:50:47 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: page_ref: remove folio_try_get_rcu() 2024-07-25 09:50:56 +02:00
net wifi: mac80211: disable softirqs for queued frame handling 2024-07-25 09:50:57 +02:00
rust rust: kernel: require Send for Module implementations 2024-05-17 12:01:56 +02:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-23 09:24:47 +01:00
scripts kconfig: remove wrong expr_trans_bool() 2024-07-25 09:50:44 +02:00
security ima: Avoid blocking in RCU read-side critical section 2024-07-11 12:49:18 +02:00
sound ALSA: seq: ump: Skip useless ports for static blocks 2024-07-27 11:34:10 +02:00
tools selftests/bpf: Extend tcx tests to cover late tcx_entry release 2024-07-25 09:50:56 +02:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:49:11 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml
COPYING
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig
MAINTAINERS pwm: Rename pwm_apply_state() to pwm_apply_might_sleep() 2024-06-12 11:12:24 +02:00
Makefile Linux 6.6.43 2024-07-27 11:34:11 +02:00
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