Btrfs: change how we iterate bios in endio

Since dio submit has used bio_clone_fast, the submitted bio may not have a
reliable bi_vcnt, for the bio vector iterations in checksum related
functions, bio->bi_iter is not modified yet and it's safe to use
bio_for_each_segment, while for those bio vector iterations in dio read's
endio, we now save a copy of bvec_iter in struct btrfs_io_bio when cloning
bios and use the helper __bio_for_each_segment with the saved bvec_iter to
access each bvec.

Also for dio reads which don't get split, we also need to save a copy of
bio iterator in btrfs_bio_clone to let __bio_for_each_segments to access
each bvec in dio read's endio.  Note that it doesn't affect other calls of
btrfs_bio_clone() because they don't need to use this iterator.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 15 insertions, 16 deletions

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 64fcb31d7163..9f6062c82419 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -164,7 +164,8 @@ static int __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
 				   u64 logical_offset, u32 *dst, int dio)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
-	struct bio_vec *bvec;
+	struct bio_vec bvec;
+	struct bvec_iter iter;
 	struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio);
 	struct btrfs_csum_item *item = NULL;
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
@@ -177,7 +178,7 @@ static int __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
 	u64 page_bytes_left;
 	u32 diff;
 	int nblocks;
-	int count = 0, i;
+	int count = 0;
 	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
 
 	path = btrfs_alloc_path();
@@ -206,8 +207,6 @@ static int __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
 	if (bio->bi_iter.bi_size > PAGE_SIZE * 8)
 		path->reada = READA_FORWARD;
 
-	WARN_ON(bio->bi_vcnt <= 0);
-
 	/*
 	 * the free space stuff is only read when it hasn't been
 	 * updated in the current transaction.  So, we can safely
@@ -223,13 +222,13 @@ static int __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
 	if (dio)
 		offset = logical_offset;
 
-	bio_for_each_segment_all(bvec, bio, i) {
-		page_bytes_left = bvec->bv_len;
+	bio_for_each_segment(bvec, bio, iter) {
+		page_bytes_left = bvec.bv_len;
 		if (count)
 			goto next;
 
 		if (!dio)
-			offset = page_offset(bvec->bv_page) + bvec->bv_offset;
+			offset = page_offset(bvec.bv_page) + bvec.bv_offset;
 		count = btrfs_find_ordered_sum(inode, offset, disk_bytenr,
 					       (u32 *)csum, nblocks);
 		if (count)
@@ -440,15 +439,15 @@ int btrfs_csum_one_bio(struct inode *inode, struct bio *bio,
 	struct btrfs_ordered_sum *sums;
 	struct btrfs_ordered_extent *ordered = NULL;
 	char *data;
-	struct bio_vec *bvec;
+	struct bvec_iter iter;
+	struct bio_vec bvec;
 	int index;
 	int nr_sectors;
-	int i, j;
 	unsigned long total_bytes = 0;
 	unsigned long this_sum_bytes = 0;
+	int i;
 	u64 offset;
 
-	WARN_ON(bio->bi_vcnt <= 0);
 	sums = kzalloc(btrfs_ordered_sum_size(fs_info, bio->bi_iter.bi_size),
 		       GFP_NOFS);
 	if (!sums)
@@ -465,19 +464,19 @@ int btrfs_csum_one_bio(struct inode *inode, struct bio *bio,
 	sums->bytenr = (u64)bio->bi_iter.bi_sector << 9;
 	index = 0;
 
-	bio_for_each_segment_all(bvec, bio, j) {
+	bio_for_each_segment(bvec, bio, iter) {
 		if (!contig)
-			offset = page_offset(bvec->bv_page) + bvec->bv_offset;
+			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);
+		data = kmap_atomic(bvec.bv_page);
 
 		nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info,
-						 bvec->bv_len + fs_info->sectorsize
+						 bvec.bv_len + fs_info->sectorsize
 						 - 1);
 
 		for (i = 0; i < nr_sectors; i++) {
@@ -504,12 +503,12 @@ int btrfs_csum_one_bio(struct inode *inode, struct bio *bio,
 					+ total_bytes;
 				index = 0;
 
-				data = kmap_atomic(bvec->bv_page);
+				data = kmap_atomic(bvec.bv_page);
 			}
 
 			sums->sums[index] = ~(u32)0;
 			sums->sums[index]
-				= btrfs_csum_data(data + bvec->bv_offset
+				= btrfs_csum_data(data + bvec.bv_offset
 						+ (i * fs_info->sectorsize),
 						sums->sums[index],
 						fs_info->sectorsize);