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

[Mohamed Khalfella <mkhalfella@purestorage.com>]

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?

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
>