btrfs: don't access the bio directly in btrfs_csum_one_bio

Use bio_for_each_segment_all to iterate over the segments instead.
This requires a bit of reshuffling so that we only lookup up the ordered
item once inside the bio_for_each_segment_all loop.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 43418c0..fad3804 100644 (file)
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -447,13 +447,12 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
                       struct bio *bio, u64 file_start, int contig)
 {
        struct btrfs_ordered_sum *sums;
-       struct btrfs_ordered_extent *ordered;
+       struct btrfs_ordered_extent *ordered = NULL;
        char *data;
-       struct bio_vec *bvec = bio->bi_io_vec;
-       int bio_index = 0;
+       struct bio_vec *bvec;
        int index;
        int nr_sectors;
-       int i;
+       int i, j;
        unsigned long total_bytes = 0;
        unsigned long this_sum_bytes = 0;
        u64 offset;
@@ -470,17 +469,20 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
        if (contig)
                offset = file_start;
        else
-               offset = page_offset(bvec->bv_page) + bvec->bv_offset;
+               offset = 0; /* shut up gcc */
 
-       ordered = btrfs_lookup_ordered_extent(inode, offset);
-       BUG_ON(!ordered); /* Logic error */
        sums->bytenr = (u64)bio->bi_iter.bi_sector << 9;
        index = 0;
 
-       while (bio_index < bio->bi_vcnt) {
+       bio_for_each_segment_all(bvec, bio, j) {
                if (!contig)
                        offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 
+               if (!ordered) {
+                       ordered = btrfs_lookup_ordered_extent(inode, offset);
+                       BUG_ON(!ordered); /* Logic error */
+               }
+
                data = kmap_atomic(bvec->bv_page);
 
                nr_sectors = BTRFS_BYTES_TO_BLKS(root->fs_info,
@@ -529,9 +531,6 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
                }
 
                kunmap_atomic(data);
-
-               bio_index++;
-               bvec++;
        }
        this_sum_bytes = 0;
        btrfs_add_ordered_sum(inode, ordered, sums);