Re: [PATCH] dm-verity: do forward error correction on metadata I/O errors

[Milan Broz]

On 2/10/25 4:04 PM, Mikulas Patocka wrote:

Do forward error correction if metadata I/O fails.

Signed-off-by: Mikulas Patocka <mpato...@redhat.com>

Not directly related to this patch, but...
please could you also increase the dm-verity version?

I just implemented support for the errors-as-corruption
dm-verity flags in veritysetup.

The version of dm-verity stayed at 1.10 for a very long, and
the IO error processing change was a functional change that we
would like to detect.
We cannot set version retrospectively, but at least now with other
changes.

(Veritysetup tries the requested flags; if activation fails,
it displays a better error message based on the detected
target version. That way it works even with backports.)

Thanks,
Milan

---
  drivers/md/dm-verity-target.c |   19 +++++++++++++++++--
  1 file changed, 17 insertions(+), 2 deletions(-)

Index: linux-2.6/drivers/md/dm-verity-target.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-verity-target.c        2025-02-04 
13:52:45.000000000 +0100
+++ linux-2.6/drivers/md/dm-verity-target.c     2025-02-10 15:55:42.000000000 
+0100
@@ -324,8 +324,22 @@ static int verity_verify_level(struct dm
                                                &buf, bio->bi_ioprio);
        }

- if (IS_ERR(data))

-               return PTR_ERR(data);
+       if (IS_ERR(data)) {
+               r = PTR_ERR(data);
+               data = dm_bufio_new(v->bufio, hash_block, &buf);
+               if (IS_ERR(data))
+                       return r;
+               if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA,
+                                     hash_block, data) == 0) {
+                       aux = dm_bufio_get_aux_data(buf);
+                       aux->hash_verified = 1;
+                       goto release_ok;
+               } else {
+                       dm_bufio_release(buf);
+                       dm_bufio_forget(v->bufio, hash_block);
+                       return r;
+               }
+       }

aux = dm_bufio_get_aux_data(buf); @@ -366,6 +380,7 @@ static int verity_verify_level(struct dm

                }
        }

+release_ok:

        data += offset;
        memcpy(want_digest, data, v->digest_size);
        r = 0;