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Message-ID: <3624f83b-cfb3-9b1a-8cc8-8caffba7a786@huaweicloud.com>
Date: Mon, 1 Sep 2025 10:16:36 +0800
From: Li Nan <linan666@...weicloud.com>
To: Paul Menzel <pmenzel@...gen.mpg.de>, Li Nan <linan666@...weicloud.com>
Cc: song@...nel.org, yukuai3@...wei.com, linux-raid@...r.kernel.org,
linux-kernel@...r.kernel.org, yangerkun@...wei.com, yi.zhang@...wei.com
Subject: Re: [PATCH] md: ensure consistent action state in md_do_sync
在 2025/8/30 17:51, Paul Menzel 写道:
> Dear Nan,
>
>
> Thank you for your patch.
>
> Am 30.08.25 um 11:05 schrieb linan666@...weicloud.com:
>> From: Li Nan <linan122@...wei.com>
>>
>> The 'mddev->recovery' flags can change during md_do_sync(), leading to
>> inconsistencies. For example, starting with MD_RECOVERY_RECOVER and
>> ending with MD_RECOVERY_SYNC can cause incorrect offset updates.
>
> Can you give a concrete example?
>
T1 T2
md_do_sync
action = ACTION_RECOVER
(write sysfs)
action_store
set MD_RECOVERY_SYNC
[ do recovery ]
update resync_offset
The corresponding code is:
```
if (!test_bit(MD_RECOVERY_CHECK, &mddev->recovery) &&
mddev->curr_resync > MD_RESYNC_ACTIVE) {
if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) { ->SYNC
is set, But what we do is recovery
if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
if (mddev->curr_resync >=
mddev->resync_offset) {
pr_debug("md: checkpointing %s of
%s.\n",
desc, mdname(mddev));
if (test_bit(MD_RECOVERY_ERROR,
&mddev->recovery))
mddev->resync_offset =
mddev->curr_resync_completed;
else
mddev->resync_offset =
mddev->curr_resync;
}
```
>> To avoid this, use the 'action' determined at the beginning of the
>> function instead of repeatedly checking 'mddev->recovery'.
>
> Do you have a reproducer?
>
I don't have a reproducer because reproducing it requires modifying the
kernel. The approximate steps are:
- Modify the kernel to add a delay before the above check.
- Trigger recovery by removing and adding disks.
- After recovery completes, write to the sysfs interface at the delay point
to set the sync flag.
> Add a Fixes: tag?
>
I will add it in v2.
>> Signed-off-by: Li Nan <linan122@...wei.com>
>> ---
>> drivers/md/md.c | 21 +++++++++------------
>> 1 file changed, 9 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index 6828a569e819..67cda9b64c87 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -9516,7 +9516,7 @@ void md_do_sync(struct md_thread *thread)
>> skipped = 0;
>> - if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
>> + if (action != ACTION_RESHAPE &&
>> ((mddev->curr_resync > mddev->curr_resync_completed &&
>> (mddev->curr_resync - mddev->curr_resync_completed)
>> > (max_sectors >> 4)) ||
>> @@ -9529,8 +9529,7 @@ void md_do_sync(struct md_thread *thread)
>> wait_event(mddev->recovery_wait,
>> atomic_read(&mddev->recovery_active) == 0);
>> mddev->curr_resync_completed = j;
>> - if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) &&
>> - j > mddev->resync_offset)
>> + if (action == ACTION_RESYNC && j > mddev->resync_offset)
>> mddev->resync_offset = j;
>> update_time = jiffies;
>> set_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags);
>> @@ -9646,7 +9645,7 @@ void md_do_sync(struct md_thread *thread)
>> blk_finish_plug(&plug);
>> wait_event(mddev->recovery_wait,
>> !atomic_read(&mddev->recovery_active));
>> - if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
>> + if (action != ACTION_RESHAPE &&
>> !test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
>> mddev->curr_resync >= MD_RESYNC_ACTIVE) {
>> mddev->curr_resync_completed = mddev->curr_resync;
>> @@ -9654,9 +9653,8 @@ void md_do_sync(struct md_thread *thread)
>> }
>> mddev->pers->sync_request(mddev, max_sectors, max_sectors, &skipped);
>> - if (!test_bit(MD_RECOVERY_CHECK, &mddev->recovery) &&
>> - mddev->curr_resync > MD_RESYNC_ACTIVE) {
>> - if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
>> + if (action != ACTION_CHECK && mddev->curr_resync > MD_RESYNC_ACTIVE) {
>> + if (action == ACTION_RESYNC) {
>> if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
>> if (mddev->curr_resync >= mddev->resync_offset) {
>> pr_debug("md: checkpointing %s of %s.\n",
>> @@ -9674,8 +9672,7 @@ void md_do_sync(struct md_thread *thread)
>> } else {
>> if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery))
>> mddev->curr_resync = MaxSector;
>> - if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
>> - test_bit(MD_RECOVERY_RECOVER, &mddev->recovery)) {
>> + if (action == ACTION_RECOVER) {
>
> What about `MD_RECOVERY_RESHAPE`?
>
>> rcu_read_lock();
>> rdev_for_each_rcu(rdev, mddev)
>> if (mddev->delta_disks >= 0 &&
>> @@ -9692,7 +9689,7 @@ void md_do_sync(struct md_thread *thread)
>> set_mask_bits(&mddev->sb_flags, 0,
>> BIT(MD_SB_CHANGE_PENDING) | BIT(MD_SB_CHANGE_DEVS));
>> - if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
>> + if (action == ACTION_RESHAPE &&
>> !test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
>> mddev->delta_disks > 0 &&
>> mddev->pers->finish_reshape &&
>> @@ -9709,10 +9706,10 @@ void md_do_sync(struct md_thread *thread)
>> spin_lock(&mddev->lock);
>> if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
>> /* We completed so min/max setting can be forgotten if used. */
>> - if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
>> + if (action == ACTION_REPAIR)
>> mddev->resync_min = 0;
>> mddev->resync_max = MaxSector;
>> - } else if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
>> + } else if (action == ACTION_REPAIR)
>> mddev->resync_min = mddev->curr_resync_completed;
>> set_bit(MD_RECOVERY_DONE, &mddev->recovery);
>> mddev->curr_resync = MD_RESYNC_NONE;
>
> I have not fully grogged yet, what the consequence of a mismatch between
> `action`, set at the beginning, and changed flags in `&mddev->recovery` are.
>
>
> Kind regards,
>
> Paul
>
> .
--
Thanks,
Nan
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