btrfs: introduce a common helper to calculate the size of a bio

We have several call sites doing the same work to calculate the size of
a bio:

	struct bio_vec *bvec;
	u32 bio_size = 0;
	int i;

	bio_for_each_bvec_all(bvec, bio, i)
		bio_size += bvec->bv_len;

We can use a common helper instead of open-coding it everywhere.

This also allows us to constify the @bio_size variables used in all the
call sites.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

3 files changed, 17 insertions, 29 deletions

diff --git a/fs/btrfs/misc.h b/fs/btrfs/misc.h
index 40433a86fe49..694be6d0562a 100644
--- a/fs/btrfs/misc.h
+++ b/fs/btrfs/misc.h
@@ -53,15 +53,22 @@ static inline phys_addr_t bio_iter_phys(const struct bio *bio,
 	     (paddr = bio_iter_phys((bio), (iter)), 1);			\
 	     bio_advance_iter_single((bio), (iter), (blocksize)))
 
-/* Initialize a bvec_iter to the size of the specified bio. */
-static inline struct bvec_iter init_bvec_iter_for_bio(struct bio *bio)
+/* Can only be called on a non-cloned bio. */
+static inline u32 bio_get_size(struct bio *bio)
 {
 	struct bio_vec *bvec;
-	u32 bio_size = 0;
+	u32 ret = 0;
 	int i;
 
 	bio_for_each_bvec_all(bvec, bio, i)
-		bio_size += bvec->bv_len;
+		ret += bvec->bv_len;
+	return ret;
+}
+
+/* Initialize a bvec_iter to the size of the specified bio. */
+static inline struct bvec_iter init_bvec_iter_for_bio(struct bio *bio)
+{
+	const u32 bio_size = bio_get_size(bio);
 
 	return (struct bvec_iter) {
 		.bi_sector = 0,
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 02105d68accb..aacf5e4eb765 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -1653,12 +1653,7 @@ static int get_bio_sector_nr(struct btrfs_raid_bio *rbio, struct bio *bio)
 static void rbio_update_error_bitmap(struct btrfs_raid_bio *rbio, struct bio *bio)
 {
 	int total_sector_nr = get_bio_sector_nr(rbio, bio);
-	u32 bio_size = 0;
-	struct bio_vec *bvec;
-	int i;
-
-	bio_for_each_bvec_all(bvec, bio, i)
-		bio_size += bvec->bv_len;
+	const u32 bio_size = bio_get_size(bio);
 
 	/*
 	 * Since we can have multiple bios touching the error_bitmap, we cannot
@@ -1666,7 +1661,7 @@ static void rbio_update_error_bitmap(struct btrfs_raid_bio *rbio, struct bio *bi
 	 *
 	 * Instead use set_bit() for each bit, as set_bit() itself is atomic.
 	 */
-	for (i = total_sector_nr; i < total_sector_nr +
+	for (int i = total_sector_nr; i < total_sector_nr +
 	     (bio_size >> rbio->bioc->fs_info->sectorsize_bits); i++)
 		set_bit(i, rbio->error_bitmap);
 }
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index bc94bbc00772..0234971894fa 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -891,16 +891,11 @@ static void scrub_repair_read_endio(struct btrfs_bio *bbio)
 {
 	struct scrub_stripe *stripe = bbio->private;
 	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
-	struct bio_vec *bvec;
 	int sector_nr = calc_sector_number(stripe, bio_first_bvec_all(&bbio->bio));
-	u32 bio_size = 0;
-	int i;
+	const u32 bio_size = bio_get_size(&bbio->bio);
 
 	ASSERT(sector_nr < stripe->nr_sectors);
 
-	bio_for_each_bvec_all(bvec, &bbio->bio, i)
-		bio_size += bvec->bv_len;
-
 	if (bbio->bio.bi_status) {
 		scrub_bitmap_set_io_error(stripe, sector_nr,
 					  bio_size >> fs_info->sectorsize_bits);
@@ -1249,15 +1244,11 @@ out:
 static void scrub_read_endio(struct btrfs_bio *bbio)
 {
 	struct scrub_stripe *stripe = bbio->private;
-	struct bio_vec *bvec;
 	int sector_nr = calc_sector_number(stripe, bio_first_bvec_all(&bbio->bio));
 	int num_sectors;
-	u32 bio_size = 0;
-	int i;
+	const u32 bio_size = bio_get_size(&bbio->bio);
 
 	ASSERT(sector_nr < stripe->nr_sectors);
-	bio_for_each_bvec_all(bvec, &bbio->bio, i)
-		bio_size += bvec->bv_len;
 	num_sectors = bio_size >> stripe->bg->fs_info->sectorsize_bits;
 
 	if (bbio->bio.bi_status) {
@@ -1278,13 +1269,8 @@ static void scrub_write_endio(struct btrfs_bio *bbio)
 {
 	struct scrub_stripe *stripe = bbio->private;
 	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
-	struct bio_vec *bvec;
 	int sector_nr = calc_sector_number(stripe, bio_first_bvec_all(&bbio->bio));
-	u32 bio_size = 0;
-	int i;
-
-	bio_for_each_bvec_all(bvec, &bbio->bio, i)
-		bio_size += bvec->bv_len;
+	const u32 bio_size = bio_get_size(&bbio->bio);
 
 	if (bbio->bio.bi_status) {
 		unsigned long flags;
@@ -1293,7 +1279,7 @@ static void scrub_write_endio(struct btrfs_bio *bbio)
 		bitmap_set(&stripe->write_error_bitmap, sector_nr,
 			   bio_size >> fs_info->sectorsize_bits);
 		spin_unlock_irqrestore(&stripe->write_error_lock, flags);
-		for (i = 0; i < (bio_size >> fs_info->sectorsize_bits); i++)
+		for (int i = 0; i < (bio_size >> fs_info->sectorsize_bits); i++)
 			btrfs_dev_stat_inc_and_print(stripe->dev,
 						     BTRFS_DEV_STAT_WRITE_ERRS);
 	}