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Message-ID: <d0de7500-eac0-4d02-9b48-887cdefab4c1@fwd.mgml.me>
Date: Wed, 24 Sep 2025 00:54:44 +0900
From: Kenta Akagi <k@....mgml.me>
To: Yu Kuai <hailan@...uai.org.cn>, yukuai1@...weicloud.com, song@...nel.org,
mtkaczyk@...nel.org, shli@...com, jgq516@...il.com
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
yukuai3@...wei.com, Kenta Akagi <k@....mgml.me>
Subject: Re: [PATCH v4 4/9] md/raid1,raid10: Don't set MD_BROKEN on failfast
bio failure
Hi,
On 2025/09/20 18:51, Yu Kuai wrote:
> Hi,
>
> 在 2025/9/20 14:30, Kenta Akagi 写道:
>> Hi,
>>
>> I have changed my email address because our primary MX server
>> suddenly started rejecting non-DKIM mail.
>>
>> On 2025/09/19 10:36, Yu Kuai wrote:
>>> Hi,
>>>
>>> 在 2025/9/18 23:22, Kenta Akagi 写道:
>>>>>> @@ -470,7 +470,7 @@ static void raid1_end_write_request(struct bio *bio)
>>>>>> (bio->bi_opf & MD_FAILFAST) &&
>>>>>> /* We never try FailFast to WriteMostly devices */
>>>>>> !test_bit(WriteMostly, &rdev->flags)) {
>>>>>> - md_error(r1_bio->mddev, rdev);
>>>>>> + md_bio_failure_error(r1_bio->mddev, rdev, bio);
>>>>>> }
>>>>> Can following check of faulty replaced with return value?
>>>> In the case where raid1_end_write_request is called for a non-failfast IO,
>>>> and the rdev has already been marked Faulty by another bio, it must not retry too.
>>>> I think it would be simpler not to use a return value here.
>>> You can just add Faulty check inside md_bio_failure_error() as well, and both
>>> failfast and writemostly check.
>> Sorry, I'm not sure I understand this part.
>> In raid1_end_write_request, this code path is also used for a regular bio,
>> not only for FailFast.
>>
>> You mean to change md_bio_failure_error as follows:
>> * If the rdev is Faulty, immediately return true.
>> * If the given bio is Failfast and the rdev is not the lastdev, call md_error.
>> * If the given bio is not Failfast, do nothing and return false.
>
> Yes, doesn't that apply to all the callers?
It's difficult because the flow differs depending on the function.
For example, in raid1_end_write_request, if rdev and bio are Failfast but not Writemostly,
it calls md_error, and then performs a something if it is Faulty regardless
of whether it is Failfast or not. This flow is specific to raid1_end_write_request.
Other functions that need to be changed to md_bio_failure_error are handle_read_error
and fix_sync_read_error, but the path for determining whether these are Faulty,
regardless of whether they are Failfast, is not exists there functions.
It may be possible with some refactoring,
but I think raid1_end_write_request current style, that is
if(Failfast) md_bio_failure_error();
if(Faulty) something;
would be better because We can see at a glance what is happening.
BTW, fix_sync_read_error can use the return value of md_bio_failure_error as
suggested. so I'll revise it as follows:
@@ -2167,8 +2174,7 @@ static int fix_sync_read_error(struct r1bio *r1_bio)
if (test_bit(FailFast, &rdev->flags)) {
/* Don't try recovering from here - just fail it
* ... unless it is the last working device of course */
- md_bio_failure_error(mddev, rdev, bio);
- if (test_bit(Faulty, &rdev->flags))
+ if (md_bio_failure_error(mddev, rdev, bio))
/* Don't try to read from here, but make sure
* put_buf does it's thing
*/
>
>>
>> And then apply this?
>> This is complicated. Wouldn't it be better to keep the Faulty check as it is?
>>
>> @@ -466,18 +466,12 @@ static void raid1_end_write_request(struct bio *bio)
>> set_bit(MD_RECOVERY_NEEDED, &
>> conf->mddev->recovery);
>>
>> - if (test_bit(FailFast, &rdev->flags) &&
>> - (bio->bi_opf & MD_FAILFAST) &&
>> - /* We never try FailFast to WriteMostly devices */
>> - !test_bit(WriteMostly, &rdev->flags)) {
>> - md_error(r1_bio->mddev, rdev);
>> - }
>> -
>> /*
>> * When the device is faulty, it is not necessary to
>> * handle write error.
>> */
>> - if (!test_bit(Faulty, &rdev->flags))
>> + if (!test_bit(Faulty, &rdev->flags) ||
>> + !md_bio_failure_error(r1_bio->mddev, rdev, bio))
>> set_bit(R1BIO_WriteError, &r1_bio->state);
>> else {
>> /* Finished with this branch */
>
> Faulty is set with lock held, so check Faulty with lock held as well can
> prevent rdev to be Faulty concurrently, and this check can be added to all
> callers, I think.
>
>>
>> Or do you mean a fix like this?
>>
>> @@ -466,23 +466,24 @@ static void raid1_end_write_request(struct bio *bio)
>> set_bit(MD_RECOVERY_NEEDED, &
>> conf->mddev->recovery);
>>
>> - if (test_bit(FailFast, &rdev->flags) &&
>> - (bio->bi_opf & MD_FAILFAST) &&
>> - /* We never try FailFast to WriteMostly devices */
>> - !test_bit(WriteMostly, &rdev->flags)) {
>> - md_error(r1_bio->mddev, rdev);
>> - }
>> -
>> /*
>> * When the device is faulty, it is not necessary to
>> * handle write error.
>> */
>> - if (!test_bit(Faulty, &rdev->flags))
>> - set_bit(R1BIO_WriteError, &r1_bio->state);
>> - else {
>> + if (test_bit(Faulty, &rdev->flags) ||
>> + (
>> + test_bit(FailFast, &rdev->flags) &&
>> + (bio->bi_opf & MD_FAILFAST) &&
>> + /* We never try FailFast to WriteMostly devices */
>> + !test_bit(WriteMostly, &rdev->flags) &&
>> + md_bio_failure_error(r1_bio->mddev, rdev, bio)
>> + )
>> + ) {
>> /* Finished with this branch */
>> r1_bio->bios[mirror] = NULL;
>> to_put = bio;
>> + } else {
>> + set_bit(R1BIO_WriteError, &r1_bio->state);
>> }
>> } else {
>> /*
>
> No, this just make code even more unreadable.
Understood.
Thanks,
Akagi
>
> Thanks,
> Kuai
>
>> Thanks,
>> Akagi
>>
>>> Thanks,
>>> Kuai
>>>
>>>
>>>
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