linux-stable.git/drivers/md/raid5.c, branch linux-5.4.y Linux kernel stable tree md/raid5: avoid BUG_ON() while continue reshape after reassembling 2024-08-19T03:33:46+00:00 Yu Kuai yukuai3@huawei.com 2024-06-11T13:22:51+00:00 6b33c468d543f6a83de2d61f09fec74b27e19fd2 [ Upstream commit 305a5170dc5cf3d395bb4c4e9239bca6d0b54b49 ] Currently, mdadm support --revert-reshape to abort the reshape while reassembling, as the test 07revert-grow. However, following BUG_ON() can be triggerred by the test: kernel BUG at drivers/md/raid5.c:6278! invalid opcode: 0000 [#1] PREEMPT SMP PTI irq event stamp: 158985 CPU: 6 PID: 891 Comm: md0_reshape Not tainted 6.9.0-03335-g7592a0b0049a #94 RIP: 0010:reshape_request+0x3f1/0xe60 Call Trace: <TASK> raid5_sync_request+0x43d/0x550 md_do_sync+0xb7a/0x2110 md_thread+0x294/0x2b0 kthread+0x147/0x1c0 ret_from_fork+0x59/0x70 ret_from_fork_asm+0x1a/0x30 </TASK> Root cause is that --revert-reshape update the raid_disks from 5 to 4, while reshape position is still set, and after reassembling the array, reshape position will be read from super block, then during reshape the checking of 'writepos' that is caculated by old reshape position will fail. Fix this panic the easy way first, by converting the BUG_ON() to WARN_ON(), and stop the reshape if checkings fail. Noted that mdadm must fix --revert-shape as well, and probably md/raid should enhance metadata validation as well, however this means reassemble will fail and there must be user tools to fix the wrong metadata. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Song Liu <song@kernel.org> Link: https://lore.kernel.org/r/20240611132251.1967786-13-yukuai1@huaweicloud.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 305a5170dc5cf3d395bb4c4e9239bca6d0b54b49 ]

Currently, mdadm support --revert-reshape to abort the reshape while
reassembling, as the test 07revert-grow. However, following BUG_ON()
can be triggerred by the test:

kernel BUG at drivers/md/raid5.c:6278!
invalid opcode: 0000 [#1] PREEMPT SMP PTI
irq event stamp: 158985
CPU: 6 PID: 891 Comm: md0_reshape Not tainted 6.9.0-03335-g7592a0b0049a #94
RIP: 0010:reshape_request+0x3f1/0xe60
Call Trace:
 <TASK>
 raid5_sync_request+0x43d/0x550
 md_do_sync+0xb7a/0x2110
 md_thread+0x294/0x2b0
 kthread+0x147/0x1c0
 ret_from_fork+0x59/0x70
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Root cause is that --revert-reshape update the raid_disks from 5 to 4,
while reshape position is still set, and after reassembling the array,
reshape position will be read from super block, then during reshape the
checking of 'writepos' that is caculated by old reshape position will
fail.

Fix this panic the easy way first, by converting the BUG_ON() to
WARN_ON(), and stop the reshape if checkings fail.

Noted that mdadm must fix --revert-shape as well, and probably md/raid
should enhance metadata validation as well, however this means
reassemble will fail and there must be user tools to fix the wrong
metadata.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240611132251.1967786-13-yukuai1@huaweicloud.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
md/raid5: fix deadlock that raid5d() wait for itself to clear MD_SB_CHANGE_PENDING 2024-06-16T11:28:50+00:00 Yu Kuai yukuai3@huawei.com 2024-03-22T08:10:05+00:00 634ba3c97ec413cb10681c7b196db43ee461ecf4 commit 151f66bb618d1fd0eeb84acb61b4a9fa5d8bb0fa upstream. Xiao reported that lvm2 test lvconvert-raid-takeover.sh can hang with small possibility, the root cause is exactly the same as commit bed9e27baf52 ("Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d"") However, Dan reported another hang after that, and junxiao investigated the problem and found out that this is caused by plugged bio can't issue from raid5d(). Current implementation in raid5d() has a weird dependence: 1) md_check_recovery() from raid5d() must hold 'reconfig_mutex' to clear MD_SB_CHANGE_PENDING; 2) raid5d() handles IO in a deadloop, until all IO are issued; 3) IO from raid5d() must wait for MD_SB_CHANGE_PENDING to be cleared; This behaviour is introduce before v2.6, and for consequence, if other context hold 'reconfig_mutex', and md_check_recovery() can't update super_block, then raid5d() will waste one cpu 100% by the deadloop, until 'reconfig_mutex' is released. Refer to the implementation from raid1 and raid10, fix this problem by skipping issue IO if MD_SB_CHANGE_PENDING is still set after md_check_recovery(), daemon thread will be woken up when 'reconfig_mutex' is released. Meanwhile, the hang problem will be fixed as well. Fixes: 5e2cf333b7bd ("md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d") Cc: stable@vger.kernel.org # v5.19+ Reported-and-tested-by: Dan Moulding <dan@danm.net> Closes: https://lore.kernel.org/all/20240123005700.9302-1-dan@danm.net/ Investigated-by: Junxiao Bi <junxiao.bi@oracle.com> Signed-off-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20240322081005.1112401-1-yukuai1@huaweicloud.com Signed-off-by: Song Liu <song@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 151f66bb618d1fd0eeb84acb61b4a9fa5d8bb0fa upstream.

Xiao reported that lvm2 test lvconvert-raid-takeover.sh can hang with
small possibility, the root cause is exactly the same as commit
bed9e27baf52 ("Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d"")

However, Dan reported another hang after that, and junxiao investigated
the problem and found out that this is caused by plugged bio can't issue
from raid5d().

Current implementation in raid5d() has a weird dependence:

1) md_check_recovery() from raid5d() must hold 'reconfig_mutex' to clear
   MD_SB_CHANGE_PENDING;
2) raid5d() handles IO in a deadloop, until all IO are issued;
3) IO from raid5d() must wait for MD_SB_CHANGE_PENDING to be cleared;

This behaviour is introduce before v2.6, and for consequence, if other
context hold 'reconfig_mutex', and md_check_recovery() can't update
super_block, then raid5d() will waste one cpu 100% by the deadloop, until
'reconfig_mutex' is released.

Refer to the implementation from raid1 and raid10, fix this problem by
skipping issue IO if MD_SB_CHANGE_PENDING is still set after
md_check_recovery(), daemon thread will be woken up when 'reconfig_mutex'
is released. Meanwhile, the hang problem will be fixed as well.

Fixes: 5e2cf333b7bd ("md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d")
Cc: stable@vger.kernel.org # v5.19+
Reported-and-tested-by: Dan Moulding <dan@danm.net>
Closes: https://lore.kernel.org/all/20240123005700.9302-1-dan@danm.net/
Investigated-by: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240322081005.1112401-1-yukuai1@huaweicloud.com
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Revert "Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d"" 2024-04-13T10:51:25+00:00 Song Liu song@kernel.org 2024-01-25T08:21:31+00:00 0b949dc2257d3154d45df17bce14c0483c602219 [ Upstream commit 3445139e3a594be77eff48bc17eff67cf983daed ] This reverts commit bed9e27baf52a09b7ba2a3714f1e24e17ced386d. The original set [1][2] was expected to undo a suboptimal fix in [2], and replace it with a better fix [1]. However, as reported by Dan Moulding [2] causes an issue with raid5 with journal device. Revert [2] for now to close the issue. We will follow up on another issue reported by Juxiao Bi, as [2] is expected to fix it. We believe this is a good trade-off, because the latter issue happens less freqently. In the meanwhile, we will NOT revert [1], as it contains the right logic. [1] commit d6e035aad6c0 ("md: bypass block throttle for superblock update") [2] commit bed9e27baf52 ("Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d"") Reported-by: Dan Moulding <dan@danm.net> Closes: https://lore.kernel.org/linux-raid/20240123005700.9302-1-dan@danm.net/ Fixes: bed9e27baf52 ("Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d"") Cc: stable@vger.kernel.org # v5.19+ Cc: Junxiao Bi <junxiao.bi@oracle.com> Cc: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Song Liu <song@kernel.org> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20240125082131.788600-1-song@kernel.org Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 3445139e3a594be77eff48bc17eff67cf983daed ]

This reverts commit bed9e27baf52a09b7ba2a3714f1e24e17ced386d.

The original set [1][2] was expected to undo a suboptimal fix in [2], and
replace it with a better fix [1]. However, as reported by Dan Moulding [2]
causes an issue with raid5 with journal device.

Revert [2] for now to close the issue. We will follow up on another issue
reported by Juxiao Bi, as [2] is expected to fix it. We believe this is a
good trade-off, because the latter issue happens less freqently.

In the meanwhile, we will NOT revert [1], as it contains the right logic.

[1] commit d6e035aad6c0 ("md: bypass block throttle for superblock update")
[2] commit bed9e27baf52 ("Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d"")

Reported-by: Dan Moulding <dan@danm.net>
Closes: https://lore.kernel.org/linux-raid/20240123005700.9302-1-dan@danm.net/
Fixes: bed9e27baf52 ("Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d"")
Cc: stable@vger.kernel.org # v5.19+
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240125082131.788600-1-song@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Revert "md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d" 2024-02-23T07:25:13+00:00 Junxiao Bi junxiao.bi@oracle.com 2023-11-08T18:22:16+00:00 7f71d9817cea3582daa2e903596461f5f5d0c022 [ Upstream commit bed9e27baf52a09b7ba2a3714f1e24e17ced386d ] This reverts commit 5e2cf333b7bd5d3e62595a44d598a254c697cd74. That commit introduced the following race and can cause system hung. md_write_start: raid5d: // mddev->in_sync == 1 set "MD_SB_CHANGE_PENDING" // running before md_write_start wakeup it waiting "MD_SB_CHANGE_PENDING" cleared >>>>>>>>> hung wakeup mddev->thread ... waiting "MD_SB_CHANGE_PENDING" cleared >>>> hung, raid5d should clear this flag but get hung by same flag. The issue reverted commit fixing is fixed by last patch in a new way. Fixes: 5e2cf333b7bd ("md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d") Cc: stable@vger.kernel.org # v5.19+ Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Song Liu <song@kernel.org> Link: https://lore.kernel.org/r/20231108182216.73611-2-junxiao.bi@oracle.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit bed9e27baf52a09b7ba2a3714f1e24e17ced386d ]

This reverts commit 5e2cf333b7bd5d3e62595a44d598a254c697cd74.

That commit introduced the following race and can cause system hung.

 md_write_start:             raid5d:
 // mddev->in_sync == 1
 set "MD_SB_CHANGE_PENDING"
                            // running before md_write_start wakeup it
                             waiting "MD_SB_CHANGE_PENDING" cleared
                             >>>>>>>>> hung
 wakeup mddev->thread
 ...
 waiting "MD_SB_CHANGE_PENDING" cleared
 >>>> hung, raid5d should clear this flag
 but get hung by same flag.

The issue reverted commit fixing is fixed by last patch in a new way.

Fixes: 5e2cf333b7bd ("md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d")
Cc: stable@vger.kernel.org # v5.19+
Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20231108182216.73611-2-junxiao.bi@oracle.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
treewide: Remove uninitialized_var() usage 2023-06-09T08:29:01+00:00 Kees Cook keescook@chromium.org 2020-06-03T20:09:38+00:00 0638dcc7e75fbb766761e7b4694d0f0f141bbbd1 commit 3f649ab728cda8038259d8f14492fe400fbab911 upstream. Using uninitialized_var() is dangerous as it papers over real bugs[1] (or can in the future), and suppresses unrelated compiler warnings (e.g. "unused variable"). If the compiler thinks it is uninitialized, either simply initialize the variable or make compiler changes. In preparation for removing[2] the[3] macro[4], remove all remaining needless uses with the following script: git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \ xargs perl -pi -e \ 's/\buninitialized_var\(([^\)]+)\)/\1/g; s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;' drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid pathological white-space. No outstanding warnings were found building allmodconfig with GCC 9.3.0 for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64, alpha, and m68k. [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/ [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/ [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/ [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ Reviewed-by: Leon Romanovsky <leonro@mellanox.com> # drivers/infiniband and mlx4/mlx5 Acked-by: Jason Gunthorpe <jgg@mellanox.com> # IB Acked-by: Kalle Valo <kvalo@codeaurora.org> # wireless drivers Reviewed-by: Chao Yu <yuchao0@huawei.com> # erofs Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 3f649ab728cda8038259d8f14492fe400fbab911 upstream.

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

In preparation for removing[2] the[3] macro[4], remove all remaining
needless uses with the following script:

git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \
	xargs perl -pi -e \
		's/\buninitialized_var\(([^\)]+)\)/\1/g;
		 s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;'

drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid
pathological white-space.

No outstanding warnings were found building allmodconfig with GCC 9.3.0
for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64,
alpha, and m68k.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Reviewed-by: Leon Romanovsky <leonro@mellanox.com> # drivers/infiniband and mlx4/mlx5
Acked-by: Jason Gunthorpe <jgg@mellanox.com> # IB
Acked-by: Kalle Valo <kvalo@codeaurora.org> # wireless drivers
Reviewed-by: Chao Yu <yuchao0@huawei.com> # erofs
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
md: update the optimal I/O size on reshape 2023-05-17T09:35:44+00:00 Christoph Hellwig hch@lst.de 2020-09-24T06:51:33+00:00 fb3f2f2fa0f3d34f51b0a645014865f56077c908 [ Upstream commit 16ef510139315a2147ee7525796f8dbd4e4b7864 ] The raid5 and raid10 drivers currently update the read-ahead size, but not the optimal I/O size on reshape. To prepare for deriving the read-ahead size from the optimal I/O size make sure it is updated as well. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Acked-by: Song Liu <song@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk> Stable-dep-of: f0ddb83da3cb ("md/raid10: fix memleak of md thread") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 16ef510139315a2147ee7525796f8dbd4e4b7864 ]

The raid5 and raid10 drivers currently update the read-ahead size,
but not the optimal I/O size on reshape.  To prepare for deriving the
read-ahead size from the optimal I/O size make sure it is updated
as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: f0ddb83da3cb ("md/raid10: fix memleak of md thread")
Signed-off-by: Sasha Levin <sashal@kernel.org>
md/raid5: Wait for MD_SB_CHANGE_PENDING in raid5d 2022-10-26T11:22:57+00:00 Logan Gunthorpe logang@deltatee.com 2022-09-21T16:28:37+00:00 1c00bb624cd084e2006520ad0edacaff0fb941c4 [ Upstream commit 5e2cf333b7bd5d3e62595a44d598a254c697cd74 ] A complicated deadlock exists when using the journal and an elevated group_thrtead_cnt. It was found with loop devices, but its not clear whether it can be seen with real disks. The deadlock can occur simply by writing data with an fio script. When the deadlock occurs, multiple threads will hang in different ways: 1) The group threads will hang in the blk-wbt code with bios waiting to be submitted to the block layer: io_schedule+0x70/0xb0 rq_qos_wait+0x153/0x210 wbt_wait+0x115/0x1b0 io_schedule+0x70/0xb0 rq_qos_wait+0x153/0x210 wbt_wait+0x115/0x1b0 __rq_qos_throttle+0x38/0x60 blk_mq_submit_bio+0x589/0xcd0 wbt_wait+0x115/0x1b0 __rq_qos_throttle+0x38/0x60 blk_mq_submit_bio+0x589/0xcd0 __submit_bio+0xe6/0x100 submit_bio_noacct_nocheck+0x42e/0x470 submit_bio_noacct+0x4c2/0xbb0 ops_run_io+0x46b/0x1a30 handle_stripe+0xcd3/0x36b0 handle_active_stripes.constprop.0+0x6f6/0xa60 raid5_do_work+0x177/0x330 Or: io_schedule+0x70/0xb0 rq_qos_wait+0x153/0x210 wbt_wait+0x115/0x1b0 __rq_qos_throttle+0x38/0x60 blk_mq_submit_bio+0x589/0xcd0 __submit_bio+0xe6/0x100 submit_bio_noacct_nocheck+0x42e/0x470 submit_bio_noacct+0x4c2/0xbb0 flush_deferred_bios+0x136/0x170 raid5_do_work+0x262/0x330 2) The r5l_reclaim thread will hang in the same way, submitting a bio to the block layer: io_schedule+0x70/0xb0 rq_qos_wait+0x153/0x210 wbt_wait+0x115/0x1b0 __rq_qos_throttle+0x38/0x60 blk_mq_submit_bio+0x589/0xcd0 __submit_bio+0xe6/0x100 submit_bio_noacct_nocheck+0x42e/0x470 submit_bio_noacct+0x4c2/0xbb0 submit_bio+0x3f/0xf0 md_super_write+0x12f/0x1b0 md_update_sb.part.0+0x7c6/0xff0 md_update_sb+0x30/0x60 r5l_do_reclaim+0x4f9/0x5e0 r5l_reclaim_thread+0x69/0x30b However, before hanging, the MD_SB_CHANGE_PENDING flag will be set for sb_flags in r5l_write_super_and_discard_space(). This flag will never be cleared because the submit_bio() call never returns. 3) Due to the MD_SB_CHANGE_PENDING flag being set, handle_stripe() will do no processing on any pending stripes and re-set STRIPE_HANDLE. This will cause the raid5d thread to enter an infinite loop, constantly trying to handle the same stripes stuck in the queue. The raid5d thread has a blk_plug that holds a number of bios that are also stuck waiting seeing the thread is in a loop that never schedules. These bios have been accounted for by blk-wbt thus preventing the other threads above from continuing when they try to submit bios. --Deadlock. To fix this, add the same wait_event() that is used in raid5_do_work() to raid5d() such that if MD_SB_CHANGE_PENDING is set, the thread will schedule and wait until the flag is cleared. The schedule action will flush the plug which will allow the r5l_reclaim thread to continue, thus preventing the deadlock. However, md_check_recovery() calls can also clear MD_SB_CHANGE_PENDING from the same thread and can thus deadlock if the thread is put to sleep. So avoid waiting if md_check_recovery() is being called in the loop. It's not clear when the deadlock was introduced, but the similar wait_event() call in raid5_do_work() was added in 2017 by this commit: 16d997b78b15 ("md/raid5: simplfy delaying of writes while metadata is updated.") Link: https://lore.kernel.org/r/7f3b87b6-b52a-f737-51d7-a4eec5c44112@deltatee.com Signed-off-by: Logan Gunthorpe <logang@deltatee.com> Signed-off-by: Song Liu <song@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 5e2cf333b7bd5d3e62595a44d598a254c697cd74 ]

A complicated deadlock exists when using the journal and an elevated
group_thrtead_cnt. It was found with loop devices, but its not clear
whether it can be seen with real disks. The deadlock can occur simply
by writing data with an fio script.

When the deadlock occurs, multiple threads will hang in different ways:

 1) The group threads will hang in the blk-wbt code with bios waiting to
    be submitted to the block layer:

        io_schedule+0x70/0xb0
        rq_qos_wait+0x153/0x210
        wbt_wait+0x115/0x1b0
        io_schedule+0x70/0xb0
        rq_qos_wait+0x153/0x210
        wbt_wait+0x115/0x1b0
        __rq_qos_throttle+0x38/0x60
        blk_mq_submit_bio+0x589/0xcd0
        wbt_wait+0x115/0x1b0
        __rq_qos_throttle+0x38/0x60
        blk_mq_submit_bio+0x589/0xcd0
        __submit_bio+0xe6/0x100
        submit_bio_noacct_nocheck+0x42e/0x470
        submit_bio_noacct+0x4c2/0xbb0
        ops_run_io+0x46b/0x1a30
        handle_stripe+0xcd3/0x36b0
        handle_active_stripes.constprop.0+0x6f6/0xa60
        raid5_do_work+0x177/0x330

    Or:
        io_schedule+0x70/0xb0
        rq_qos_wait+0x153/0x210
        wbt_wait+0x115/0x1b0
        __rq_qos_throttle+0x38/0x60
        blk_mq_submit_bio+0x589/0xcd0
        __submit_bio+0xe6/0x100
        submit_bio_noacct_nocheck+0x42e/0x470
        submit_bio_noacct+0x4c2/0xbb0
        flush_deferred_bios+0x136/0x170
        raid5_do_work+0x262/0x330

 2) The r5l_reclaim thread will hang in the same way, submitting a
    bio to the block layer:

        io_schedule+0x70/0xb0
        rq_qos_wait+0x153/0x210
        wbt_wait+0x115/0x1b0
        __rq_qos_throttle+0x38/0x60
        blk_mq_submit_bio+0x589/0xcd0
        __submit_bio+0xe6/0x100
        submit_bio_noacct_nocheck+0x42e/0x470
        submit_bio_noacct+0x4c2/0xbb0
        submit_bio+0x3f/0xf0
        md_super_write+0x12f/0x1b0
        md_update_sb.part.0+0x7c6/0xff0
        md_update_sb+0x30/0x60
        r5l_do_reclaim+0x4f9/0x5e0
        r5l_reclaim_thread+0x69/0x30b

    However, before hanging, the MD_SB_CHANGE_PENDING flag will be
    set for sb_flags in r5l_write_super_and_discard_space(). This
    flag will never be cleared because the submit_bio() call never
    returns.

 3) Due to the MD_SB_CHANGE_PENDING flag being set, handle_stripe()
    will do no processing on any pending stripes and re-set
    STRIPE_HANDLE. This will cause the raid5d thread to enter an
    infinite loop, constantly trying to handle the same stripes
    stuck in the queue.

    The raid5d thread has a blk_plug that holds a number of bios
    that are also stuck waiting seeing the thread is in a loop
    that never schedules. These bios have been accounted for by
    blk-wbt thus preventing the other threads above from
    continuing when they try to submit bios. --Deadlock.

To fix this, add the same wait_event() that is used in raid5_do_work()
to raid5d() such that if MD_SB_CHANGE_PENDING is set, the thread will
schedule and wait until the flag is cleared. The schedule action will
flush the plug which will allow the r5l_reclaim thread to continue,
thus preventing the deadlock.

However, md_check_recovery() calls can also clear MD_SB_CHANGE_PENDING
from the same thread and can thus deadlock if the thread is put to
sleep. So avoid waiting if md_check_recovery() is being called in the
loop.

It's not clear when the deadlock was introduced, but the similar
wait_event() call in raid5_do_work() was added in 2017 by this
commit:

    16d997b78b15 ("md/raid5: simplfy delaying of writes while metadata
                   is updated.")

Link: https://lore.kernel.org/r/7f3b87b6-b52a-f737-51d7-a4eec5c44112@deltatee.com
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
md/raid5: Ensure stripe_fill happens on non-read IO with journal 2022-10-26T11:22:39+00:00 Logan Gunthorpe logang@deltatee.com 2022-08-25T15:46:27+00:00 f8ba29ae237e9be431301cb310a8cd0b6ce72b6f [ Upstream commit e2eed85bc75138a9eeb63863d20f8904ac42a577 ] When doing degrade/recover tests using the journal a kernel BUG is hit at drivers/md/raid5.c:4381 in handle_parity_checks5(): BUG_ON(!test_bit(R5_UPTODATE, &dev->flags)); This was found to occur because handle_stripe_fill() was skipped for stripes in the journal due to a condition in that function. Thus blocks were not fetched and R5_UPTODATE was not set when the code reached handle_parity_checks5(). To fix this, don't skip handle_stripe_fill() unless the stripe is for read. Fixes: 07e83364845e ("md/r5cache: shift complex rmw from read path to write path") Link: https://lore.kernel.org/linux-raid/e05c4239-41a9-d2f7-3cfa-4aa9d2cea8c1@deltatee.com/ Suggested-by: Song Liu <song@kernel.org> Signed-off-by: Logan Gunthorpe <logang@deltatee.com> Signed-off-by: Song Liu <song@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit e2eed85bc75138a9eeb63863d20f8904ac42a577 ]

When doing degrade/recover tests using the journal a kernel BUG
is hit at drivers/md/raid5.c:4381 in handle_parity_checks5():

  BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));

This was found to occur because handle_stripe_fill() was skipped
for stripes in the journal due to a condition in that function.
Thus blocks were not fetched and R5_UPTODATE was not set when
the code reached handle_parity_checks5().

To fix this, don't skip handle_stripe_fill() unless the stripe is
for read.

Fixes: 07e83364845e ("md/r5cache: shift complex rmw from read path to write path")
Link: https://lore.kernel.org/linux-raid/e05c4239-41a9-d2f7-3cfa-4aa9d2cea8c1@deltatee.com/
Suggested-by: Song Liu <song@kernel.org>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
drivers:md:fix a potential use-after-free bug 2022-08-25T09:18:35+00:00 Wentao_Liang Wentao_Liang_g@163.com 2022-07-28T11:39:19+00:00 f5d46f1b47f65da1faf468277b261eb78c8e25b5 [ Upstream commit 104212471b1c1817b311771d817fb692af983173 ] In line 2884, "raid5_release_stripe(sh);" drops the reference to sh and may cause sh to be released. However, sh is subsequently used in lines 2886 "if (sh->batch_head && sh != sh->batch_head)". This may result in an use-after-free bug. It can be fixed by moving "raid5_release_stripe(sh);" to the bottom of the function. Signed-off-by: Wentao_Liang <Wentao_Liang_g@163.com> Signed-off-by: Song Liu <song@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 104212471b1c1817b311771d817fb692af983173 ]

In line 2884, "raid5_release_stripe(sh);" drops the reference to sh and
may cause sh to be released. However, sh is subsequently used in lines
2886 "if (sh->batch_head && sh != sh->batch_head)". This may result in an
use-after-free bug.

It can be fixed by moving "raid5_release_stripe(sh);" to the bottom of
the function.

Signed-off-by: Wentao_Liang <Wentao_Liang_g@163.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
dm raid: fix KASAN warning in raid5_add_disks 2022-07-07T15:36:48+00:00 Mikulas Patocka mpatocka@redhat.com 2022-06-29T17:40:57+00:00 f157bd9cf377a947fdb7035e69466b6ecdc17c17 commit 617b365872a247480e9dcd50a32c8d1806b21861 upstream. There's a KASAN warning in raid5_add_disk when running the LVM testsuite. The warning happens in the test lvconvert-raid-reshape-linear_to_raid6-single-type.sh. We fix the warning by verifying that rdev->saved_raid_disk is within limits. Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 617b365872a247480e9dcd50a32c8d1806b21861 upstream.

There's a KASAN warning in raid5_add_disk when running the LVM testsuite.
The warning happens in the test
lvconvert-raid-reshape-linear_to_raid6-single-type.sh. We fix the warning
by verifying that rdev->saved_raid_disk is within limits.

Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>