[PATCH v4 11/11] scsi: add support for user-meta interface

[Anuj Gupta]

On Thu, Oct 17, 2024 at 04:39:18PM +0200, Christoph Hellwig wrote:
> On Thu, Oct 17, 2024 at 05:09:23PM +0530, Anuj Gupta wrote:
> > This snippet prevents a scenario where a apptag check is specified without
> > a reftag check and vice-versa, which is not possible for scsi[1].
> > But for
> > block layer generated integrity apptag check (BIP_CHECK_APPTAG) is not
> > specified. When scsi drive is formatted with type1/2 PI, block layer would
> > specify refcheck but not appcheck. Hence, these I/O's would fail. Do you
> > see how we can handle this?
> 
> Well, this is also related to difference in capability checking.

Right.

> Just curious, do you have any user of the more fine grained checking
> in NVMe?  If not we could support the SCSI semantics only and emulate
> them using the fine grained NVMe semantics and have no portability
> problems.
 
We can choose to support scsi semantics only and expose only the valid
scsi combinations to userspace i.e.

1. no check
2. guard check only
3. ref + app check only
4. guard + ref + app check

Something like this [*] on top of this series, untested though. Does
this align with what you have in mind?

[*]

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index 24fad9b6f3ec..2ca27910770b 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -308,12 +308,10 @@ static void bio_uio_meta_to_bip(struct bio *bio, struct uio_meta *meta)
 {
 	struct bio_integrity_payload *bip = bio_integrity(bio);
 
-	if (meta->flags & BLK_INTEGRITY_CHK_GUARD)
+	if (meta->flags & IO_INTEGRITY_CHK_GUARD)
 		bip->bip_flags |= BIP_CHECK_GUARD;
-	if (meta->flags & BLK_INTEGRITY_CHK_APPTAG)
-		bip->bip_flags |= BIP_CHECK_APPTAG;
-	if (meta->flags & BLK_INTEGRITY_CHK_REFTAG)
-		bip->bip_flags |= BIP_CHECK_REFTAG;
+	if (meta->flags & IO_INTEGRITY_CHK_REF_APP)
+		bip->bip_flags |= BIP_CHECK_REFTAG | BIP_CHECK_APPTAG;
 
 	bip->app_tag = meta->app_tag;
 }
@@ -329,9 +327,9 @@ int bio_integrity_map_iter(struct bio *bio, struct uio_meta *meta)
 		return -EINVAL;
 
 	/* should fit into two bytes */
-	BUILD_BUG_ON(BLK_INTEGRITY_VALID_FLAGS >= (1 << 16));
+	BUILD_BUG_ON(IO_INTEGRITY_VALID_FLAGS >= (1 << 16));
 
-	if (meta->flags && (meta->flags & ~BLK_INTEGRITY_VALID_FLAGS))
+	if (meta->flags && (meta->flags & ~IO_INTEGRITY_VALID_FLAGS))
 		return -EINVAL;
 
 	/*
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 753971770733..714700f9826e 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -40,6 +40,15 @@
 #define BLOCK_SIZE_BITS 10
 #define BLOCK_SIZE (1<<BLOCK_SIZE_BITS)
 
+/*
+ * flags for integrity meta
+ */
+#define IO_INTEGRITY_CHK_GUARD		(1U << 0) /* enforce guard check */
+#define IO_INTEGRITY_CHK_REF_APP	(1U << 1) /* enforce ref and app check */
+
+#define IO_INTEGRITY_VALID_FLAGS (IO_INTEGRITY_CHK_GUARD | \
+				  IO_INTEGRITY_CHK_REF_APP)
+
 #define SEEK_SET	0	/* seek relative to beginning of file */
 #define SEEK_CUR	1	/* seek relative to current file position */
 #define SEEK_END	2	/* seek relative to end of file */