btrfs: simplify bvec iteration in index_one_bio()

Flatten the two loops by open coding bio_for_each_segment() and advancing
the iterator one sector at a time.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Qu Wenruo <wqu@suse.com>
[ Fix a bug that @offset is not increased. ]
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index bd6350e8f5c51e9a9105193bfb6275c2c43e6930..6e1d9cdd59c185ea539da7ac1a6ffc07410886ac 100644 (file)
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -1195,23 +1195,22 @@ static int rbio_add_io_sector(struct btrfs_raid_bio *rbio,
 static void index_one_bio(struct btrfs_raid_bio *rbio, struct bio *bio)
 {
        const u32 sectorsize = rbio->bioc->fs_info->sectorsize;
-       struct bio_vec bvec;
-       struct bvec_iter iter;
+       const u32 sectorsize_bits = rbio->bioc->fs_info->sectorsize_bits;
+       struct bvec_iter iter = bio->bi_iter;
        u32 offset = (bio->bi_iter.bi_sector << SECTOR_SHIFT) -
                     rbio->bioc->full_stripe_logical;
 
-       bio_for_each_segment(bvec, bio, iter) {
-               u32 bvec_offset;
+       while (iter.bi_size) {
+               unsigned int index = (offset >> sectorsize_bits);
+               struct sector_ptr *sector = &rbio->bio_sectors[index];
+               struct bio_vec bv = bio_iter_iovec(bio, iter);
 
-               for (bvec_offset = 0; bvec_offset < bvec.bv_len;
-                    bvec_offset += sectorsize, offset += sectorsize) {
-                       int index = offset / sectorsize;
-                       struct sector_ptr *sector = &rbio->bio_sectors[index];
+               sector->page = bv.bv_page;
+               sector->pgoff = bv.bv_offset;
+               ASSERT(sector->pgoff < PAGE_SIZE);
 
-                       sector->page = bvec.bv_page;
-                       sector->pgoff = bvec.bv_offset + bvec_offset;
-                       ASSERT(sector->pgoff < PAGE_SIZE);
-               }
+               bio_advance_iter_single(bio, &iter, sectorsize);
+               offset += sectorsize;
        }
 }