Re: [PATCH] md/raid1,raid10: don't fail devices for invalid IO errors

["Tomáš Trnka" <trnka@scm.com>]

On Thursday, 16 April 2026 16:03:45, CEST Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> BLK_STS_INVAL indicates the IO request itself was invalid, not that the
> device has failed. When raid1 treats this as a device error, it retries
> on alternate mirrors which fail the same way, eventually exceeding the
> read error threshold and removing the device from the array.
> 
> This happens when stacking configurations bypass bio_split_to_limits()
> in the IO path: dm-raid calls md_handle_request() directly without going
> through md_submit_bio(), skipping the alignment validation that would
> otherwise reject invalid bios early. The invalid bio reaches the
> lower block layers, which fail the bio with  BLK_STS_INVAL, and raid1
> wrongly interprets this as a device failure.
> 
> Add BLK_STS_INVAL to raid1_should_handle_error() so that invalid IO
> errors are propagated back to the caller rather than triggering device
> removal. This is consistent with the previous kernel behavior when
> alignment checks were done earlier in the direct-io path.
> 
> Fixes: 5ff3f74e145adc7 ("block: simplify direct io validity check")
> Link: https://lore.kernel.org/linux-block/2982107.4sosBPzcNG@electra/
> Reported-by: Tomáš Trnka <trnka@scm.com>
> Signed-off-by: Keith Busch <kbusch@kernel.org>

Tested-by: Tomáš Trnka <trnka@scm.com>

> ---
>  drivers/md/raid1-10.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/raid1-10.c b/drivers/md/raid1-10.c
> index c33099925f230..56a56a4da4f83 100644
> --- a/drivers/md/raid1-10.c
> +++ b/drivers/md/raid1-10.c
> @@ -293,8 +293,13 @@ static inline bool raid1_should_read_first(struct mddev
> *mddev, * bio with REQ_RAHEAD or REQ_NOWAIT can fail at anytime, before
> such IO is * submitted to the underlying disks, hence don't record
> badblocks or retry * in this case.
> + *
> + * BLK_STS_INVAL means the bio was not valid for the underlying device.
> This + * is a user error, not a device failure, so retrying or recording
> bad blocks + * would be wrong.
>   */
>  static inline bool raid1_should_handle_error(struct bio *bio)
>  {
> -	return !(bio->bi_opf & (REQ_RAHEAD | REQ_NOWAIT));
> +	return !(bio->bi_opf & (REQ_RAHEAD | REQ_NOWAIT)) &&
> +		bio->bi_status != BLK_STS_INVAL;
>  }