Re: [PATCH for-6.10 1/2] dm-crypt: stop constraining max_segment_size to PAGE_SIZE

[Ming Lei <ming.lei@redhat.com>]

On Thu, Apr 11, 2024 at 04:15:28PM -0400, Mike Snitzer wrote:
> This change effectively reverts commit 586b286b110e ("dm crypt:
> constrain crypt device's max_segment_size to PAGE_SIZE") and relies on
> block core's late bio-splitting to ensure that dm-crypt's encryption
> bios are split accordingly if they exceed the underlying device's
> limits (e.g. max_segment_size).
> 
> Commit 586b286b110e was applied as a 4.3 fix for the benefit of
> stable@ kernels 4.0+ just after block core's late bio-splitting was
> introduced in 4.3 with commit 54efd50bfd873 ("block: make
> generic_make_request handle arbitrarily sized bios"). Given block
> core's late bio-splitting it is past time that dm-crypt make use of
> it.
> 
> Also, given the recent need to revert meaningful progress that was
> attempted during the 6.9 merge window (see commit bff4b74625fe Revert
> "dm: use queue_limits_set") this change allows DM core to safely make
> use of queue_limits_set() without risk of breaking dm-crypt on NVMe.
> Though it should be noted this commit isn't a prereq for reinstating
> DM core's use of queue_limits_set() because blk_validate_limits() was
> made less strict with commit b561ea56a264 ("block: allow device to
> have both virt_boundary_mask and max segment size").
> 
> Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks,
Ming