On 6/24/20 1:58 AM, Song Liu wrote:

On Tue, Jun 16, 2020 at 2:25 AM Guoqing Jiang
[off-list ref] wrote:

quoted

We tried to only put the head sh of batch list to handle_list, then the
handle_stripe doesn't handle other members in the batch list. However,
we still got the calltrace in break_stripe_batch_list.

[593764.644269] stripe state: 2003
kernel: [593764.644299] ------------[ cut here ]------------
kernel: [593764.644308] WARNING: CPU: 12 PID: 856 at drivers/md/raid5.c:4625 break_stripe_batch_list+0x203/0x240 [raid456]
[...]
kernel: [593764.644363] Call Trace:
kernel: [593764.644370]  handle_stripe+0x907/0x20c0 [raid456]
kernel: [593764.644376]  ? __wake_up_common_lock+0x89/0xc0
kernel: [593764.644379]  handle_active_stripes.isra.57+0x35f/0x570 [raid456]
kernel: [593764.644382]  ? raid5_wakeup_stripe_thread+0x96/0x1f0 [raid456]
kernel: [593764.644385]  raid5d+0x480/0x6a0 [raid456]
kernel: [593764.644390]  ? md_thread+0x11f/0x160
kernel: [593764.644392]  md_thread+0x11f/0x160
kernel: [593764.644394]  ? wait_woken+0x80/0x80
kernel: [593764.644396]  kthread+0xfc/0x130
kernel: [593764.644398]  ? find_pers+0x70/0x70
kernel: [593764.644399]  ? kthread_create_on_node+0x70/0x70
kernel: [593764.644401]  ret_from_fork+0x1f/0x30

As we can see, the stripe was set with STRIPE_ACTIVE and STRIPE_HANDLE,
and only handle_stripe could set those flags then return. And since the
stipe was already in the batch list, we need to return earlier before
set the two flags.

And after dig a little about git history especially commit 3664847d95e6
("md/raid5: fix a race condition in stripe batch"), it seems the batched
stipe still could be handled by handle_stipe, then handle_stipe needs to
return earlier if clear_batch_ready to return true.

Signed-off-by: Guoqing Jiang <redacted>
---
Another alternative would be just not warn if STRIPE_ACTIVE is valid for
the batched list.

What do you think?

This patch looks good to me (haven't tested yet). Let's try with this one.

Ok, pls let me know if there is issue during test.

And do you want a new patch to reflect which I clarified for the line
number and kernel version?

Thanks,
Guoqing