[PATCH 3/5] block: Reduce the size of struct blk_integrity

[Martin K. Petersen]

The per-device properties in the blk_integrity structure were previously
unsigned short. However, most of the values fit inside a char. The only
exception is the data interval size and we can work around that by
storing it as a power of two.

This cuts the size of the dynamic portion of blk_integrity in half.

Signed-off-by: Martin K. Petersen <martin.petersen at oracle.com>
Reported-by: Christoph Hellwig <hch at lst.de>
---
 block/bio-integrity.c  | 4 ++--
 block/blk-integrity.c  | 6 +++---
 include/linux/blkdev.h | 8 ++++----
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index f09531130cff..4da7fbc28845 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -197,7 +197,7 @@ EXPORT_SYMBOL(bio_integrity_enabled);
 static inline unsigned int bio_integrity_intervals(struct blk_integrity *bi,
 						   unsigned int sectors)
 {
-	return sectors >> (ilog2(bi->interval) - 9);
+	return sectors >> (bi->interval_exp - 9);
 }
 
 static inline unsigned int bio_integrity_bytes(struct blk_integrity *bi,
@@ -224,7 +224,7 @@ static int bio_integrity_process(struct bio *bio,
 		bip->bip_vec->bv_offset;
 
 	iter.disk_name = bio->bi_bdev->bd_disk->disk_name;
-	iter.interval = bi->interval;
+	iter.interval = 1 << bi->interval_exp;
 	iter.seed = bip_get_seed(bip);
 	iter.prot_buf = prot_buf;
 
diff --git a/block/blk-integrity.c b/block/blk-integrity.c
index 5e5280d58c61..70ba9389d0dd 100644
--- a/block/blk-integrity.c
+++ b/block/blk-integrity.c
@@ -155,10 +155,10 @@ int blk_integrity_compare(struct gendisk *gd1, struct gendisk *gd2)
 	if (!b1 || !b2)
 		return -1;
 
-	if (b1->interval != b2->interval) {
+	if (b1->interval_exp != b2->interval_exp) {
 		pr_err("%s: %s/%s protection interval %u != %u\n",
 		       __func__, gd1->disk_name, gd2->disk_name,
-		       b1->interval, b2->interval);
+		       1 << b1->interval_exp, 1 << b2->interval_exp);
 		return -1;
 	}
 
@@ -437,7 +437,7 @@ int blk_integrity_register(struct gendisk *disk, struct blk_integrity *template)
 		kobject_uevent(&disk->integrity_kobj, KOBJ_ADD);
 
 		bi->flags |= BLK_INTEGRITY_VERIFY | BLK_INTEGRITY_GENERATE;
-		bi->interval = queue_logical_block_size(disk->queue);
+		bi->interval_exp = ilog2(queue_logical_block_size(disk->queue));
 		disk->integrity = bi;
 	} else
 		bi = disk->integrity;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 4fbb3b9f7f2e..c01ce2f7168b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1435,10 +1435,10 @@ struct blk_integrity_profile {
 
 struct blk_integrity {
 	struct blk_integrity_profile	*profile;
-	unsigned short			flags;
-	unsigned short			tuple_size;
-	unsigned short			interval;
-	unsigned short			tag_size;
+	unsigned char			flags;
+	unsigned char			tuple_size;
+	unsigned char			interval_exp;
+	unsigned char			tag_size;
 };
 
 extern bool blk_integrity_is_initialized(struct gendisk *);
-- 
2.4.3