dm integrity: count and display checksum failures

This changes DM integrity to count the number of checksum failures and
report the counter in response to STATUSTYPE_INFO request (via 'dmsetup
status').

Signed-off-by: Mikulas Patocka <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

drivers/md/dm-integrity.c

···
 	struct alg_spec internal_hash_alg;
 	struct alg_spec journal_crypt_alg;
 	struct alg_spec journal_mac_alg;
+
+	atomic64_t number_of_mismatches;
 };
 
 struct dm_integrity_range {
···
 
 static void dm_integrity_io_error(struct dm_integrity_c *ic, const char *msg, int err)
 {
+	if (err == -EILSEQ)
+		atomic64_inc(&ic->number_of_mismatches);
 	if (!cmpxchg(&ic->failed, 0, err))
 		DMERR("Error on %s: %d", msg, err);
 }
···
 					DMERR("Checksum failed at sector 0x%llx",
 					      (unsigned long long)(sector - ((r + ic->tag_size - 1) / ic->tag_size)));
 					r = -EILSEQ;
+					atomic64_inc(&ic->number_of_mismatches);
 				}
 				if (likely(checksums != checksums_onstack))
 					kfree(checksums);
···
 
 	switch (type) {
 	case STATUSTYPE_INFO:
-		result[0] = '\0';
+		DMEMIT("%llu", (unsigned long long)atomic64_read(&ic->number_of_mismatches));
 		break;
 
 	case STATUSTYPE_TABLE: {
···
 	bio_list_init(&ic->flush_bio_list);
 	init_waitqueue_head(&ic->copy_to_journal_wait);
 	init_completion(&ic->crypto_backoff);
+	atomic64_set(&ic->number_of_mismatches, 0);
 
 	r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &ic->dev);
 	if (r) {
···
 
 static struct target_type integrity_target = {
 	.name			= "integrity",
-	.version		= {1, 0, 0},
+	.version		= {1, 1, 0},
 	.module			= THIS_MODULE,
 	.features		= DM_TARGET_SINGLETON | DM_TARGET_INTEGRITY,
 	.ctr			= dm_integrity_ctr,