dm integrity: use discard support when recalculating

If we have discard support we don't have to recalculate hash - we can
just fill the metadata with the discard pattern.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-integrity.c

@@ -2689,6 +2689,7 @@ static void integrity_recalc(struct work_struct *w)
 	if (unlikely(dm_integrity_failed(ic)))
 		goto err;
 
+	if (!ic->discard) {
 		io_req.bi_op = REQ_OP_READ;
 		io_req.bi_op_flags = 0;
 		io_req.mem.type = DM_IO_VMA;
@@ -2710,6 +2711,9 @@ static void integrity_recalc(struct work_struct *w)
 			integrity_sector_checksum(ic, logical_sector + i, ic->recalc_buffer + (i << SECTOR_SHIFT), t);
 			t += ic->tag_size;
 		}
+	} else {
+		t = ic->recalc_tags + (n_sectors >> ic->sb->log2_sectors_per_block) * ic->tag_size;
+	}
 
 	metadata_block = get_metadata_sector_and_offset(ic, area, offset, &metadata_offset);
 
@@ -4364,12 +4368,14 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 			goto bad;
 		}
 		INIT_WORK(&ic->recalc_work, integrity_recalc);
+		if (!ic->discard) {
 			ic->recalc_buffer = vmalloc(RECALC_SECTORS << SECTOR_SHIFT);
 			if (!ic->recalc_buffer) {
 				ti->error = "Cannot allocate buffer for recalculating";
 				r = -ENOMEM;
 				goto bad;
 			}
+		}
 		ic->recalc_tags = kvmalloc_array(RECALC_SECTORS >> ic->sb->log2_sectors_per_block,
 						 ic->tag_size, GFP_KERNEL);
 		if (!ic->recalc_tags) {
@@ -4377,6 +4383,9 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 			r = -ENOMEM;
 			goto bad;
 		}
+		if (ic->discard)
+			memset(ic->recalc_tags, DISCARD_FILLER,
+			       (RECALC_SECTORS >> ic->sb->log2_sectors_per_block) * ic->tag_size);
 	} else {
 		if (ic->sb->flags & cpu_to_le32(SB_FLAG_RECALCULATING)) {
 			ti->error = "Recalculate can only be specified with internal_hash";
@@ -4570,7 +4579,7 @@ static void dm_integrity_dtr(struct dm_target *ti)
 
 static struct target_type integrity_target = {
 	.name			= "integrity",
-	.version		= {1, 8, 0},
+	.version		= {1, 9, 0},
 	.module			= THIS_MODULE,
 	.features		= DM_TARGET_SINGLETON | DM_TARGET_INTEGRITY,
 	.ctr			= dm_integrity_ctr,