dm-verity-fec: fix corrected block count stat

commit 48640c8 upstream.

dm_verity_fec::corrected seems to have been intended to count the number
of corrected blocks.  However, it actually counted the number of calls
to fec_decode_bufs() that corrected at least one error.  That's not the
same thing.  For example, in low-memory situations correcting a single
block can require many calls to fec_decode_bufs().

Fix it to count corrected blocks instead.

Fixes: ae97648 ("dm verity fec: Expose corrected block count via status")
Cc: Shubhankar Mishra <shubhankarm@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Eric Biggers

drivers/md/dm-verity-fec.c

@@ -163,11 +163,9 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
 	if (r < 0 && neras)
 		DMERR_LIMIT("%s: FEC %llu: failed to correct: %d",
 			    v->data_dev->name, (unsigned long long)rsb, r);
-	else if (r > 0) {
+	else if (r > 0)
 		DMWARN_LIMIT("%s: FEC %llu: corrected %d errors",
 			     v->data_dev->name, (unsigned long long)rsb, r);
-		atomic64_inc(&v->fec->corrected);
-	}
 
 	return r;
 }
@@ -439,6 +437,7 @@ int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
 	}
 
 	memcpy(dest, fio->output, 1 << v->data_dev_block_bits);
+	atomic64_inc(&v->fec->corrected);
 
 done:
 	fio->level--;