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Message-ID: <3d07a8fd-3b5e-dc68-4c32-6c0dcd0c1264@huaweicloud.com>
Date: Fri, 2 Sep 2022 16:14:25 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Yu Kuai <yukuai1@...weicloud.com>,
Logan Gunthorpe <logang@...tatee.com>, song@...nel.org
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
yi.zhang@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH -next 2/3] md/raid10: convert resync_lock to use seqlock
Hi, Logan
在 2022/09/02 9:21, Yu Kuai 写道:
> Hi,
>
> 在 2022/09/02 2:41, Logan Gunthorpe 写道:
>> Hi,
>>
>> On 2022-08-29 07:15, Yu Kuai wrote:
>>> From: Yu Kuai <yukuai3@...wei.com>
>>>
>>> Currently, wait_barrier() will hold 'resync_lock' to read
>>> 'conf->barrier',
>>> and io can't be dispatched until 'barrier' is dropped.
>>>
>>> Since holding the 'barrier' is not common, convert 'resync_lock' to use
>>> seqlock so that holding lock can be avoided in fast path.
>>>
>>> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
>>
>> I've found some lockdep issues starting with this patch in md-next while
>> running mdadm tests (specifically 00raid10 when run about 10 times in a
>> row).
>>
>> I've seen a couple different lock dep errors. The first seems to be
>> reproducible on this patch, then it possibly changes to the second on
>> subsequent patches. Not sure exactly.
>>
>
> Thanks for the test,
>
> I think this is false positive because of the special usage here,
>
> for example, in raise_barrier():
>
> write_seqlock_irq
> spin_lock_irq();
> lock_acquire
> do_write_seqcount_begin
> seqcount_acquire
>
> wait_event_lock_irq_cmd
> spin_unlock_irq -> lock is released while seqcount is still hold
> if other context hold the lock again, lockdep
> will trigger warning.
> ...
> spin_lock_irq
>
> write_sequnlock_irq
>
> Functionality should be ok, I'll try to find a way to prevent such
> warning.
Can you try the following patch? I'm running mdadm tests myself and I
didn't see any problems yet.
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 2f7c8bef6dc2..317bd862f40a 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -940,16 +940,16 @@ static void raise_barrier(struct r10conf *conf,
int force)
BUG_ON(force && !conf->barrier);
/* Wait until no block IO is waiting (unless 'force') */
- wait_event_lock_irq(conf->wait_barrier, force || !conf->nr_waiting,
- conf->resync_lock.lock);
+ wait_event_seqlock_irq(conf->wait_barrier, force ||
!conf->nr_waiting,
+ conf->resync_lock);
/* block any new IO from starting */
WRITE_ONCE(conf->barrier, conf->barrier + 1);
/* Now wait for all pending IO to complete */
- wait_event_lock_irq(conf->wait_barrier,
- !atomic_read(&conf->nr_pending) &&
conf->barrier < RESYNC_DEPTH,
- conf->resync_lock.lock);
+ wait_event_seqlock_irq(conf->wait_barrier,
+ !atomic_read(&conf->nr_pending) &&
+ conf->barrier < RESYNC_DEPTH,
conf->resync_lock);
write_sequnlock_irq(&conf->resync_lock);
}
@@ -1007,7 +1007,7 @@ static bool wait_barrier(struct r10conf *conf,
bool nowait)
ret = false;
} else {
raid10_log(conf->mddev, "wait barrier");
- wait_event_lock_irq(conf->wait_barrier,
+ wait_event_seqlock_irq(conf->wait_barrier,
!conf->barrier ||
(atomic_read(&conf->nr_pending) &&
bio_list &&
@@ -1020,7 +1020,7 @@ static bool wait_barrier(struct r10conf *conf,
bool nowait)
test_bit(MD_RECOVERY_RUNNING,
&conf->mddev->recovery) &&
conf->nr_queued > 0),
- conf->resync_lock.lock);
+ conf->resync_lock);
}
conf->nr_waiting--;
if (!conf->nr_waiting)
@@ -1058,10 +1058,9 @@ static void freeze_array(struct r10conf *conf,
int extra)
conf->array_freeze_pending++;
WRITE_ONCE(conf->barrier, conf->barrier + 1);
conf->nr_waiting++;
- wait_event_lock_irq_cmd(conf->wait_barrier,
+ wait_event_seqlock_irq_cmd(conf->wait_barrier,
atomic_read(&conf->nr_pending) ==
conf->nr_queued+extra,
- conf->resync_lock.lock,
- flush_pending_writes(conf));
+ conf->resync_lock,
flush_pending_writes(conf));
conf->array_freeze_pending--;
write_sequnlock_irq(&conf->resync_lock);
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 58cfbf81447c..97d6b378e40c 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -977,6 +977,13 @@ extern int do_wait_intr_irq(wait_queue_head_t *,
wait_queue_entry_t *);
schedule();
\
spin_lock_irq(&lock))
+#define __wait_event_seqlock_irq(wq_head, condition, lock, cmd)
\
+ (void)___wait_event(wq_head, condition, TASK_UNINTERRUPTIBLE, 0,
0, \
+ write_sequnlock_irq(&lock);
\
+ cmd;
\
+ schedule();
\
+ write_seqlock_irq(&lock))
+
/**
* wait_event_lock_irq_cmd - sleep until a condition gets true. The
* condition is checked under the lock. This
@@ -1007,6 +1014,13 @@ do {
\
__wait_event_lock_irq(wq_head, condition, lock, cmd);
\
} while (0)
+#define wait_event_seqlock_irq_cmd(wq_head, condition, lock, cmd)
\
+do {
\
+ if (condition)
\
+ break;
\
+ __wait_event_seqlock_irq(wq_head, condition, lock, cmd);
\
+} while (0)
+
/**
* wait_event_lock_irq - sleep until a condition gets true. The
* condition is checked under the lock. This
@@ -1034,6 +1048,12 @@ do {
\
__wait_event_lock_irq(wq_head, condition, lock, );
\
} while (0)
+#define wait_event_seqlock_irq(wq_head, condition, lock)
\
+do {
\
+ if (condition)
\
+ break;
\
+ __wait_event_seqlock_irq(wq_head, condition, lock, );
\
+} while (0)
#define __wait_event_interruptible_lock_irq(wq_head, condition, lock,
cmd) \
___wait_event(wq_head, condition, TASK_INTERRUPTIBLE, 0, 0,
\
>
> Thanks,
> Kuai
>> I haven't dug into it too deeply, but hopefully it can be fixed easily.
>>
>> Logan
>>
>> --
>>
>>
>> ================================
>> WARNING: inconsistent lock state
>> 6.0.0-rc2-eid-vmlocalyes-dbg-00023-gfd68041d2fd2 #2604 Not tainted
>> --------------------------------
>> inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
>> fsck.ext3/1695 [HC0[0]:SC0[0]:HE0:SE1] takes:
>> ffff8881049b0120 (&____s->seqcount#10){+.?.}-{0:0}, at:
>> raid10_read_request+0x21f/0x760
>> (raid10.c:1134)
>>
>> {IN-SOFTIRQ-W} state was registered at:
>> lock_acquire+0x183/0x440
>> lower_barrier+0x5e/0xd0
>> end_sync_request+0x178/0x180
>> end_sync_write+0x193/0x380
>> bio_endio+0x346/0x3a0
>> blk_update_request+0x1eb/0x7c0
>> blk_mq_end_request+0x30/0x50
>> lo_complete_rq+0xb7/0x100
>> blk_complete_reqs+0x77/0x90
>> blk_done_softirq+0x38/0x40
>> __do_softirq+0x10c/0x650
>> run_ksoftirqd+0x48/0x80
>> smpboot_thread_fn+0x302/0x400
>> kthread+0x18c/0x1c0
>> ret_from_fork+0x1f/0x30
>>
>> irq event stamp: 8930
>> hardirqs last enabled at (8929): [<ffffffff96df8351>]
>> _raw_spin_unlock_irqrestore+0x31/0x60
>> hardirqs last disabled at (8930): [<ffffffff96df7fc5>]
>> _raw_spin_lock_irq+0x75/0x90
>> softirqs last enabled at (6768): [<ffffffff9554970e>]
>> __irq_exit_rcu+0xfe/0x150
>> softirqs last disabled at (6757): [<ffffffff9554970e>]
>> __irq_exit_rcu+0xfe/0x150
>>
>> other info that might help us debug this:
>> Possible unsafe locking scenario:
>>
>> CPU0
>> ----
>> lock(&____s->seqcount#10);
>> <Interrupt>
>> lock(&____s->seqcount#10);
>>
>> *** DEADLOCK ***
>>
>> 2 locks held by fsck.ext3/1695:
>> #0: ffff8881007d0930 (mapping.invalidate_lock#2){++++}-{3:3}, at:
>> page_cache_ra_unbounded+0xaf/0x250
>> #1: ffff8881049b0120 (&____s->seqcount#10){+.?.}-{0:0}, at:
>> raid10_read_request+0x21f/0x760
>>
>> stack backtrace:
>> CPU: 0 PID: 1695 Comm: fsck.ext3 Not tainted
>> 6.0.0-rc2-eid-vmlocalyes-dbg-00023-gfd68041d2fd2 #2604
>> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2
>> 04/01/2014
>> Call Trace:
>> <TASK>
>> dump_stack_lvl+0x5a/0x74
>> dump_stack+0x10/0x12
>> print_usage_bug.part.0+0x233/0x246
>> mark_lock.part.0.cold+0x73/0x14f
>> mark_held_locks+0x71/0xa0
>> lockdep_hardirqs_on_prepare+0x158/0x230
>> trace_hardirqs_on+0x34/0x100
>> _raw_spin_unlock_irq+0x28/0x60
>> wait_barrier+0x4a6/0x720
>> raid10.c:1004
>> raid10_read_request+0x21f/0x760
>> raid10_make_request+0x2d6/0x2160
>> md_handle_request+0x3f3/0x5b0
>> md_submit_bio+0xd9/0x120
>> __submit_bio+0x9d/0x100
>> submit_bio_noacct_nocheck+0x1fd/0x470
>> submit_bio_noacct+0x4c2/0xbb0
>> submit_bio+0x3f/0xf0
>> mpage_readahead+0x323/0x3b0
>> blkdev_readahead+0x15/0x20
>> read_pages+0x136/0x7a0
>> page_cache_ra_unbounded+0x18d/0x250
>> page_cache_ra_order+0x2c9/0x400
>> ondemand_readahead+0x320/0x730
>> page_cache_sync_ra+0xa6/0xb0
>> filemap_get_pages+0x1eb/0xc00
>> filemap_read+0x1f1/0x770
>> blkdev_read_iter+0x164/0x310
>> vfs_read+0x467/0x5a0
>> __x64_sys_pread64+0x122/0x160
>> do_syscall_64+0x35/0x80
>> entry_SYSCALL_64_after_hwframe+0x46/0xb0
>>
>> --
>>
>> ======================================================
>> WARNING: possible circular locking dependency detected
>> 6.0.0-rc2-eid-vmlocalyes-dbg-00027-gcd6aa5181bbb #2600 Not tainted
>> ------------------------------------------------------
>> systemd-udevd/292 is trying to acquire lock:
>> ffff88817b644170 (&(&conf->resync_lock)->lock){....}-{2:2}, at:
>> wait_barrier+0x4fe/0x770
>>
>> but task is already holding lock:
>> ffff88817b644120 (&____s->seqcount#11){+.+.}-{0:0}, at:
>> raid10_read_request+0x21f/0x760
>> raid10.c:1140 wait_barrier()
>> raid10.c:1204 regular_request_wait()
>>
>>
>>
>> which lock already depends on the new lock.
>>
>>
>> the existing dependency chain (in reverse order) is:
>>
>> -> #1 (&____s->seqcount#11){+.+.}-{0:0}:
>> raise_barrier+0xe0/0x300
>> raid10.c:940 write_seqlock_irq()
>> raid10_sync_request+0x629/0x4750
>> raid10.c:3689 raise_barrire()
>> md_do_sync.cold+0x8ec/0x1491
>> md_thread+0x19d/0x2d0
>> kthread+0x18c/0x1c0
>> ret_from_fork+0x1f/0x30
>>
>> -> #0 (&(&conf->resync_lock)->lock){....}-{2:2}:
>> __lock_acquire+0x1cb4/0x3170
>> lock_acquire+0x183/0x440
>> _raw_spin_lock_irq+0x4d/0x90
>> wait_barrier+0x4fe/0x770
>> raid10_read_request+0x21f/0x760
>> raid10.c:1140 wait_barrier()
>> raid10.c:1204 regular_request_wait()
>> raid10_make_request+0x2d6/0x2190
>> md_handle_request+0x3f3/0x5b0
>> md_submit_bio+0xd9/0x120
>> __submit_bio+0x9d/0x100
>> submit_bio_noacct_nocheck+0x1fd/0x470
>> submit_bio_noacct+0x4c2/0xbb0
>> submit_bio+0x3f/0xf0
>> submit_bh_wbc+0x270/0x2a0
>> block_read_full_folio+0x37c/0x580
>> blkdev_read_folio+0x18/0x20
>> filemap_read_folio+0x3f/0x110
>> do_read_cache_folio+0x13b/0x2c0
>> read_cache_folio+0x42/0x50
>> read_part_sector+0x74/0x1c0
>> read_lba+0x176/0x2a0
>> efi_partition+0x1ce/0xdd0
>> bdev_disk_changed+0x2e7/0x6a0
>> blkdev_get_whole+0xd2/0x140
>> blkdev_get_by_dev.part.0+0x37f/0x570
>> blkdev_get_by_dev+0x51/0x60
>> disk_scan_partitions+0xad/0xf0
>> blkdev_common_ioctl+0x3f3/0xdf0
>> blkdev_ioctl+0x1e1/0x450
>> __x64_sys_ioctl+0xc0/0x100
>> do_syscall_64+0x35/0x80
>> entry_SYSCALL_64_after_hwframe+0x46/0xb0
>>
>> other info that might help us debug this:
>>
>> Possible unsafe locking scenario:
>>
>> CPU0 CPU1
>> ---- ----
>> lock(&____s->seqcount#11);
>> lock(&(&conf->resync_lock)->lock);
>> lock(&____s->seqcount#11);
>> lock(&(&conf->resync_lock)->lock);
>>
>> *** DEADLOCK ***
>>
>> 2 locks held by systemd-udevd/292:
>> #0: ffff88817a532528 (&disk->open_mutex){+.+.}-{3:3}, at:
>> blkdev_get_by_dev.part.0+0x180/0x570
>> #1: ffff88817b644120 (&____s->seqcount#11){+.+.}-{0:0}, at:
>> raid10_read_request+0x21f/0x760
>>
>> stack backtrace:
>> CPU: 3 PID: 292 Comm: systemd-udevd Not tainted
>> 6.0.0-rc2-eid-vmlocalyes-dbg-00027-gcd6aa5181bbb #2600
>> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2
>> 04/01/2014
>> Call Trace:
>> <TASK>
>> dump_stack_lvl+0x5a/0x74
>> dump_stack+0x10/0x12
>> print_circular_bug.cold+0x146/0x14b
>> check_noncircular+0x1ff/0x250
>> __lock_acquire+0x1cb4/0x3170
>> lock_acquire+0x183/0x440
>> _raw_spin_lock_irq+0x4d/0x90
>> wait_barrier+0x4fe/0x770
>> raid10_read_request+0x21f/0x760
>> raid10_make_request+0x2d6/0x2190
>> md_handle_request+0x3f3/0x5b0
>> md_submit_bio+0xd9/0x120
>> __submit_bio+0x9d/0x100
>> submit_bio_noacct_nocheck+0x1fd/0x470
>> submit_bio_noacct+0x4c2/0xbb0
>> submit_bio+0x3f/0xf0
>> submit_bh_wbc+0x270/0x2a0
>> block_read_full_folio+0x37c/0x580
>> blkdev_read_folio+0x18/0x20
>> filemap_read_folio+0x3f/0x110
>> do_read_cache_folio+0x13b/0x2c0
>> read_cache_folio+0x42/0x50
>> read_part_sector+0x74/0x1c0
>> read_lba+0x176/0x2a0
>> efi_partition+0x1ce/0xdd0
>> bdev_disk_changed+0x2e7/0x6a0
>> blkdev_get_whole+0xd2/0x140
>> blkdev_get_by_dev.part.0+0x37f/0x570
>> blkdev_get_by_dev+0x51/0x60
>> disk_scan_partitions+0xad/0xf0
>> blkdev_common_ioctl+0x3f3/0xdf0
>> blkdev_ioctl+0x1e1/0x450
>> __x64_sys_ioctl+0xc0/0x100
>> do_syscall_64+0x35/0x80
>> .
>>
>
> .
>
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