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

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Message-ID: <629167c1-9be0-6128-8605-eb02391e821d@redhat.com>
Date: Mon, 10 Feb 2025 16:04:28 +0100 (CET)
From: Mikulas Patocka <mpatocka@...hat.com>
To: Akilesh Kailash <akailash@...gle.com>
cc: Sami Tolvanen <samitolvanen@...gle.com>, akailash@...gle.com, 
    kernel-team@...roid.com, Alasdair Kergon <agk@...hat.com>, 
    Mike Snitzer <snitzer@...nel.org>, Milan Broz <gmazyland@...il.com>, 
    dm-devel@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: [PATCH] dm-verity: do forward error correction on metadata I/O
 errors

Do forward error correction if metadata I/O fails.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>

---
 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;