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, 19 insertions, 16 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c2e9c51c650e..ce6a9b2cce51 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7989,6 +7989,7 @@ static int dio_read_error(struct inode *inode, struct bio *failed_bio,
 	struct bio *bio;
 	int isector;
 	int read_mode = 0;
+	int segs;
 	int ret;
 
 	BUG_ON(bio_op(failed_bio) == REQ_OP_WRITE);
@@ -8004,9 +8005,9 @@ static int dio_read_error(struct inode *inode, struct bio *failed_bio,
 		return -EIO;
 	}
 
-	if ((failed_bio->bi_vcnt > 1)
-		|| (failed_bio->bi_io_vec->bv_len
-			> btrfs_inode_sectorsize(inode)))
+	segs = bio_segments(failed_bio);
+	if (segs > 1 ||
+	    (failed_bio->bi_io_vec->bv_len > btrfs_inode_sectorsize(inode)))
 		read_mode |= REQ_FAILFAST_DEV;
 
 	isector = start - btrfs_io_bio(failed_bio)->logical;
@@ -8069,13 +8070,13 @@ static int __btrfs_correct_data_nocsum(struct inode *inode,
 				       struct btrfs_io_bio *io_bio)
 {
 	struct btrfs_fs_info *fs_info;
-	struct bio_vec *bvec;
+	struct bio_vec bvec;
+	struct bvec_iter iter;
 	struct btrfs_retry_complete done;
 	u64 start;
 	unsigned int pgoff;
 	u32 sectorsize;
 	int nr_sectors;
-	int i;
 	int ret;
 
 	fs_info = BTRFS_I(inode)->root->fs_info;
@@ -8083,17 +8084,18 @@ static int __btrfs_correct_data_nocsum(struct inode *inode,
 
 	start = io_bio->logical;
 	done.inode = inode;
+	io_bio->bio.bi_iter = io_bio->iter;
 
-	bio_for_each_segment_all(bvec, &io_bio->bio, i) {
-		nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec->bv_len);
-		pgoff = bvec->bv_offset;
+	bio_for_each_segment(bvec, &io_bio->bio, iter) {
+		nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec.bv_len);
+		pgoff = bvec.bv_offset;
 
 next_block_or_try_again:
 		done.uptodate = 0;
 		done.start = start;
 		init_completion(&done.done);
 
-		ret = dio_read_error(inode, &io_bio->bio, bvec->bv_page,
+		ret = dio_read_error(inode, &io_bio->bio, bvec.bv_page,
 				pgoff, start, start + sectorsize - 1,
 				io_bio->mirror_num,
 				btrfs_retry_endio_nocsum, &done);
@@ -8166,7 +8168,8 @@ static int __btrfs_subio_endio_read(struct inode *inode,
 				    struct btrfs_io_bio *io_bio, int err)
 {
 	struct btrfs_fs_info *fs_info;
-	struct bio_vec *bvec;
+	struct bio_vec bvec;
+	struct bvec_iter iter;
 	struct btrfs_retry_complete done;
 	u64 start;
 	u64 offset = 0;
@@ -8174,7 +8177,6 @@ static int __btrfs_subio_endio_read(struct inode *inode,
 	int nr_sectors;
 	unsigned int pgoff;
 	int csum_pos;
-	int i;
 	int ret;
 
 	fs_info = BTRFS_I(inode)->root->fs_info;
@@ -8183,15 +8185,16 @@ static int __btrfs_subio_endio_read(struct inode *inode,
 	err = 0;
 	start = io_bio->logical;
 	done.inode = inode;
+	io_bio->bio.bi_iter = io_bio->iter;
 
-	bio_for_each_segment_all(bvec, &io_bio->bio, i) {
-		nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec->bv_len);
+	bio_for_each_segment(bvec, &io_bio->bio, iter) {
+		nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec.bv_len);
 
-		pgoff = bvec->bv_offset;
+		pgoff = bvec.bv_offset;
 next_block:
 		csum_pos = BTRFS_BYTES_TO_BLKS(fs_info, offset);
 		ret = __readpage_endio_check(inode, io_bio, csum_pos,
-					bvec->bv_page, pgoff, start,
+					bvec.bv_page, pgoff, start,
 					sectorsize);
 		if (likely(!ret))
 			goto next;
@@ -8200,7 +8203,7 @@ try_again:
 		done.start = start;
 		init_completion(&done.done);
 
-		ret = dio_read_error(inode, &io_bio->bio, bvec->bv_page,
+		ret = dio_read_error(inode, &io_bio->bio, bvec.bv_page,
 				pgoff, start, start + sectorsize - 1,
 				io_bio->mirror_num,
 				btrfs_retry_endio, &done);