dm: mark targets that pass integrity data

A dm-crypt on dm-integrity device incorrectly advertises an integrity
profile on the DM crypt device. It can be seen in the files
"/sys/block/dm-*/integrity/*" that both dm-integrity and dm-crypt target
advertise the integrity profile. That is incorrect, only the
dm-integrity target should advertise the integrity profile.

A general problem in DM is that if we have a DM device that depends on
another device with an integrity profile, the upper device will always
advertise the integrity profile, even when the target driver doesn't
support handling integrity data.

Most targets don't support integrity data, so we provide a whitelist of
targets that support it (linear, delay and striped). The targets that
support passing integrity data to the lower device are marked with the
flag DM_TARGET_PASSES_INTEGRITY. The DM core will now advertise
integrity data on a DM device only if all the targets support the
integrity data.

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

drivers/md/dm-delay.c

···
 static struct target_type delay_target = {
 	.name	     = "delay",
 	.version     = {1, 2, 1},
+	.features    = DM_TARGET_PASSES_INTEGRITY,
 	.module      = THIS_MODULE,
 	.ctr	     = delay_ctr,
 	.dtr	     = delay_dtr,

drivers/md/dm-linear.c

···
 static struct target_type linear_target = {
 	.name   = "linear",
 	.version = {1, 3, 0},
+	.features = DM_TARGET_PASSES_INTEGRITY,
 	.module = THIS_MODULE,
 	.ctr    = linear_ctr,
 	.dtr    = linear_dtr,

drivers/md/dm-stripe.c

···
 static struct target_type stripe_target = {
 	.name   = "striped",
 	.version = {1, 6, 0},
+	.features = DM_TARGET_PASSES_INTEGRITY,
 	.module = THIS_MODULE,
 	.ctr    = stripe_ctr,
 	.dtr    = stripe_dtr,

drivers/md/dm-table.c

···
 	struct list_head *devices = dm_table_get_devices(t);
 	struct dm_dev_internal *dd = NULL;
 	struct gendisk *prev_disk = NULL, *template_disk = NULL;
+	unsigned i;
+
+	for (i = 0; i < dm_table_get_num_targets(t); i++) {
+		struct dm_target *ti = dm_table_get_target(t, i);
+		if (!dm_target_passes_integrity(ti->type))
+			goto no_integrity;
+	}
 
 	list_for_each_entry(dd, devices, list) {
 		template_disk = dd->dm_dev->bdev->bd_disk;

drivers/md/dm.c

···
 
 	__bio_clone_fast(clone, bio);
 
-	if (bio_integrity(bio)) {
-		int r = bio_integrity_clone(clone, bio, GFP_NOIO);
+	if (unlikely(bio_integrity(bio) != NULL)) {
+		int r;
+
+		if (unlikely(!dm_target_has_integrity(tio->ti->type) &&
+			     !dm_target_passes_integrity(tio->ti->type))) {
+			DMWARN("%s: the target %s doesn't support integrity data.",
+				dm_device_name(tio->io->md),
+				tio->ti->type->name);
+			return -EIO;
+		}
+
+		r = bio_integrity_clone(clone, bio, GFP_NOIO);
 		if (r < 0)
 			return r;
 	}
···
 	bio_advance(clone, to_bytes(sector - clone->bi_iter.bi_sector));
 	clone->bi_iter.bi_size = to_bytes(len);
 
-	if (bio_integrity(bio))
+	if (unlikely(bio_integrity(bio) != NULL))
 		bio_integrity_trim(clone, 0, len);
 
 	return 0;

include/linux/device-mapper.h

···
 #define DM_TARGET_INTEGRITY		0x00000010
 #define dm_target_has_integrity(type)	((type)->features & DM_TARGET_INTEGRITY)
 
+/*
+ * A target passes integrity data to the lower device.
+ */
+#define DM_TARGET_PASSES_INTEGRITY	0x00000020
+#define dm_target_passes_integrity(type) ((type)->features & DM_TARGET_PASSES_INTEGRITY)
+
 struct dm_target {
 	struct dm_table *table;
 	struct target_type *type;