block: Block layer data integrity support

Some block devices support verifying the integrity of requests by way
of checksums or other protection information that is submitted along
with the I/O.

This patch implements support for generating and verifying integrity
metadata, as well as correctly merging, splitting and cloning bios and
requests that have this extra information attached.

See Documentation/block/data-integrity.txt for more information.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

include/linux/blkdev.h

@@ -112,6 +112,7 @@ enum rq_flag_bits {
 	__REQ_ALLOCED,		/* request came from our alloc pool */
 	__REQ_RW_META,		/* metadata io request */
 	__REQ_COPY_USER,	/* contains copies of user pages */
+	__REQ_INTEGRITY,	/* integrity metadata has been remapped */
 	__REQ_NR_BITS,		/* stops here */
 };
 
@@ -134,6 +135,7 @@ enum rq_flag_bits {
 #define REQ_ALLOCED	(1 << __REQ_ALLOCED)
 #define REQ_RW_META	(1 << __REQ_RW_META)
 #define REQ_COPY_USER	(1 << __REQ_COPY_USER)
+#define REQ_INTEGRITY	(1 << __REQ_INTEGRITY)
 
 #define BLK_MAX_CDB	16
 
@@ -865,6 +867,109 @@ void kblockd_flush_work(struct work_struct *work);
 	MODULE_ALIAS("block-major-" __stringify(major) "-*")
 
 
+#if defined(CONFIG_BLK_DEV_INTEGRITY)
+
+#define INTEGRITY_FLAG_READ	1	/* verify data integrity on read */
+#define INTEGRITY_FLAG_WRITE	2	/* generate data integrity on write */
+
+struct blk_integrity_exchg {
+	void			*prot_buf;
+	void			*data_buf;
+	sector_t		sector;
+	unsigned int		data_size;
+	unsigned short		sector_size;
+	const char		*disk_name;
+};
+
+typedef void (integrity_gen_fn) (struct blk_integrity_exchg *);
+typedef int (integrity_vrfy_fn) (struct blk_integrity_exchg *);
+typedef void (integrity_set_tag_fn) (void *, void *, unsigned int);
+typedef void (integrity_get_tag_fn) (void *, void *, unsigned int);
+
+struct blk_integrity {
+	integrity_gen_fn	*generate_fn;
+	integrity_vrfy_fn	*verify_fn;
+	integrity_set_tag_fn	*set_tag_fn;
+	integrity_get_tag_fn	*get_tag_fn;
+
+	unsigned short		flags;
+	unsigned short		tuple_size;
+	unsigned short		sector_size;
+	unsigned short		tag_size;
+
+	const char		*name;
+
+	struct kobject		kobj;
+};
+
+extern int blk_integrity_register(struct gendisk *, struct blk_integrity *);
+extern void blk_integrity_unregister(struct gendisk *);
+extern int blk_integrity_compare(struct block_device *, struct block_device *);
+extern int blk_rq_map_integrity_sg(struct request *, struct scatterlist *);
+extern int blk_rq_count_integrity_sg(struct request *);
+
+static inline unsigned short blk_integrity_tuple_size(struct blk_integrity *bi)
+{
+	if (bi)
+		return bi->tuple_size;
+
+	return 0;
+}
+
+static inline struct blk_integrity *bdev_get_integrity(struct block_device *bdev)
+{
+	return bdev->bd_disk->integrity;
+}
+
+static inline unsigned int bdev_get_tag_size(struct block_device *bdev)
+{
+	struct blk_integrity *bi = bdev_get_integrity(bdev);
+
+	if (bi)
+		return bi->tag_size;
+
+	return 0;
+}
+
+static inline int bdev_integrity_enabled(struct block_device *bdev, int rw)
+{
+	struct blk_integrity *bi = bdev_get_integrity(bdev);
+
+	if (bi == NULL)
+		return 0;
+
+	if (rw == READ && bi->verify_fn != NULL &&
+	    test_bit(INTEGRITY_FLAG_READ, &bi->flags))
+		return 1;
+
+	if (rw == WRITE && bi->generate_fn != NULL &&
+	    test_bit(INTEGRITY_FLAG_WRITE, &bi->flags))
+		return 1;
+
+	return 0;
+}
+
+static inline int blk_integrity_rq(struct request *rq)
+{
+	BUG_ON(rq->bio == NULL);
+
+	return bio_integrity(rq->bio);
+}
+
+#else /* CONFIG_BLK_DEV_INTEGRITY */
+
+#define blk_integrity_rq(rq)			(0)
+#define blk_rq_count_integrity_sg(a)		(0)
+#define blk_rq_map_integrity_sg(a, b)		(0)
+#define bdev_get_integrity(a)			(0)
+#define bdev_get_tag_size(a)			(0)
+#define blk_integrity_compare(a, b)		(0)
+#define blk_integrity_register(a, b)		(0)
+#define blk_integrity_unregister(a)		do { } while (0);
+
+#endif /* CONFIG_BLK_DEV_INTEGRITY */
+
+
 #else /* CONFIG_BLOCK */
 /*
  * stubs for when the block layer is configured out