Re: [v3 for-next 0/3] block: delay support for error injection

[Haris Iqbal <haris.iqbal@linux.dev>]

On 10/22/26 22:23, Mohamed Khalfella wrote:
> Hello,
> 
> I wanted to use the delay injection for a test case that I am currently
> working on [1]. Are you still working on these changes?

Hello,

Yes. But currently I am moving houses and hence did not get a chance to 
look at the comments. I plan to send a v4 with changes based on the 
comments next week.

> 
> 1- https://lore.kernel.org/all/20261022185920.GA2931-mkhalfella@purestorage.com/
> 
> 
> On Tue 2026-09-29 00:16:31 +0200, Md Haris Iqbal wrote:
>> Error injection can only fail a bio today.  This adds a delay_us option so
>> that a rule can hold a bio back first, to model a slow device.  The delay
>> happens above the driver, so it tests the code waiting above the block
>> layer, not the blk-mq timeout handler.
>>
>> A delayed bio is marked with a new BIO_ERROR_INJECTED flag so the rules
>> are not applied to it again, even after a split.  Christoph asked on v2
>> to avoid the flag by allowing a delay only together with an error.  I kept
>> delay-only rules, as a slow device that succeeds is the more useful case,
>> so the flag question is still open.
>>
>> Holding a bio back reorders it against bios submitted later, which breaks
>> sequential write ordering on zoned devices.
>>
>> Patch 1 is a prep cleanup.  It moves the rejection of an unknown status
>> tag into the parser, because patch 2 makes a rule without a status valid.
>>
>> Tested in a VM.
>>
>> v1: https://lore.kernel.org/linux-block/20260827000115.128093-1-haris.iqbal@linux.dev/
>> v2: https://lore.kernel.org/linux-block/20260830012002.80275-1-haris.iqbal@linux.dev/
>>
>> Changes since v2:
>>
>>   - Patch 1: return bool, rewrite the commit message.
>>
>>   - Patch 2: drop __submit_bio_noacct_nocheck(); the flag alone stops the
>>     rules being applied again.  Log the error when a delayed bio is failed.
>>
>>   - Patch 3: trim the documentation.
>>
>> Changes since v1:
>>
>>   - Add the BIO_ERROR_INJECTED bio flag.  v1 only resubmitted a delayed bio
>>     below the injection hook, which left the remainder of a split going
>>     through the hook and matching the same rule again, so a bio was held
>>     once per split instead of once.
>>
>>   - Patch 1: tag_to_blk_status() returns an error and passes the status back
>>     through a pointer, instead of returning BLK_STS_OK for both the "OK" tag
>>     and an unknown one.  A delay-only rule has no status, so the two have to
>>     be told apart.
>>
>>   - Documentation: a delayed bio is held once rather than once per split.
>>
>> Md Haris Iqbal (3):
>>    block: Reject unknown status tags in error injection rules
>>    block: allow error injection rules to delay bios
>>    Documentation: block: document error injection delay feature
>>
>>   Documentation/block/error-injection.rst |  39 +++++-
>>   block/blk-core.c                        |  14 +-
>>   block/blk.h                             |   2 +-
>>   block/error-injection.c                 | 167 +++++++++++++++++++++---
>>   block/error-injection.h                 |   1 +
>>   include/linux/blk_types.h               |   1 +
>>   6 files changed, 192 insertions(+), 32 deletions(-)
>>
>> -- 
>> 2.53.0
>>