Re: [PATCH] dm-verity: use bdev_rw_virt() in verity_recheck()

[Eric Biggers]

On Tue, Nov 03, 2026 at 06:50:28PM +0000, Chris Wiseman wrote:
> verity_ctr() creates a dedicated dm_io_client (v->io) for every
> dm-verity target, but its only caller is verity_recheck(), which reads
> a single data block into a page from v->recheck_pool after a hash
> mismatch.  Because dm_io_client_create() preallocates a mempool of 16
> bios and 16 biovec-max (4 KiB) vectors per target, each dm-verity
> target permanently pins ~70 KiB of unreclaimable slab that a single-page
> read never uses (~2.4 MiB across 35 targets on Android, or ~4.1 MiB
> across 59 targets).
> 
> Replace dm_io() in verity_recheck() with bdev_rw_virt() and remove
> v->io.  bdev_rw_virt() puts the bio and single bio_vec on the stack and
> waits for completion, while keeping v->recheck_pool per-target.
> 
> Fixes: 9177f3c0dea6 ("dm-verity: recheck the hash after a failure")
> Link: https://lore.kernel.org/dm-devel/20250423115013.4004577-1-weilongping@xxxxxxxx/
> Signed-off-by: Chris Wiseman <chriswiseman@xxxxxxxxxx>

Reviewed-by: Eric Biggers <ebiggers@xxxxxxxxxx>

- Eric