block: Convert various code to bio_for_each_segment()

With immutable biovecs we don't want code accessing bi_io_vec directly -
the uses this patch changes weren't incorrect since they all own the
bio, but it makes the code harder to audit for no good reason - also,
this will help with multipage bvecs later.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Chris Mason <chris.mason@fusionio.com>
Cc: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Cc: Joern Engel <joern@logfs.org>
Cc: Prasad Joshi <prasadjoshi.linux@gmail.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>

4 files changed, 27 insertions, 44 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 1499b27..eac6784 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -201,18 +201,16 @@ csum_failed:
 	if (cb->errors) {
 		bio_io_error(cb->orig_bio);
 	} else {
-		int bio_index = 0;
-		struct bio_vec *bvec = cb->orig_bio->bi_io_vec;
+		int i;
+		struct bio_vec *bvec;
 
 		/*
 		 * we have verified the checksum already, set page
 		 * checked so the end_io handlers know about it
 		 */
-		while (bio_index < cb->orig_bio->bi_vcnt) {
+		bio_for_each_segment_all(bvec, cb->orig_bio, i)
 			SetPageChecked(bvec->bv_page);
-			bvec++;
-			bio_index++;
-		}
+
 		bio_endio(cb->orig_bio, 0);
 	}
 
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8072cfa..5a10c61 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -842,20 +842,17 @@ int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
 
 static int btree_csum_one_bio(struct bio *bio)
 {
-	struct bio_vec *bvec = bio->bi_io_vec;
-	int bio_index = 0;
+	struct bio_vec *bvec;
 	struct btrfs_root *root;
-	int ret = 0;
+	int i, ret = 0;
 
-	WARN_ON(bio->bi_vcnt <= 0);
-	while (bio_index < bio->bi_vcnt) {
+	bio_for_each_segment_all(bvec, bio, i) {
 		root = BTRFS_I(bvec->bv_page->mapping->host)->root;
 		ret = csum_dirty_buffer(root, bvec->bv_page);
 		if (ret)
 			break;
-		bio_index++;
-		bvec++;
 	}
+
 	return ret;
 }
 
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index ff43802..8b5f9e1 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2332,12 +2332,13 @@ int end_extent_writepage(struct page *page, int err, u64 start, u64 end)
  */
 static void end_bio_extent_writepage(struct bio *bio, int err)
 {
-	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+	struct bio_vec *bvec;
 	struct extent_io_tree *tree;
 	u64 start;
 	u64 end;
+	int i;
 
-	do {
+	bio_for_each_segment_all(bvec, bio, i) {
 		struct page *page = bvec->bv_page;
 		tree = &BTRFS_I(page->mapping->host)->io_tree;
 
@@ -2355,14 +2356,11 @@ static void end_bio_extent_writepage(struct bio *bio, int err)
 		start = page_offset(page);
 		end = start + bvec->bv_offset + bvec->bv_len - 1;
 
-		if (--bvec >= bio->bi_io_vec)
-			prefetchw(&bvec->bv_page->flags);
-
 		if (end_extent_writepage(page, err, start, end))
 			continue;
 
 		end_page_writeback(page);
-	} while (bvec >= bio->bi_io_vec);
+	}
 
 	bio_put(bio);
 }
@@ -2392,9 +2390,8 @@ endio_readpage_release_extent(struct extent_io_tree *tree, u64 start, u64 len,
  */
 static void end_bio_extent_readpage(struct bio *bio, int err)
 {
+	struct bio_vec *bvec;
 	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
-	struct bio_vec *bvec_end = bio->bi_io_vec + bio->bi_vcnt - 1;
-	struct bio_vec *bvec = bio->bi_io_vec;
 	struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
 	struct extent_io_tree *tree;
 	u64 offset = 0;
@@ -2405,11 +2402,12 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
 	u64 extent_len = 0;
 	int mirror;
 	int ret;
+	int i;
 
 	if (err)
 		uptodate = 0;
 
-	do {
+	bio_for_each_segment_all(bvec, bio, i) {
 		struct page *page = bvec->bv_page;
 		struct inode *inode = page->mapping->host;
 
@@ -2433,9 +2431,6 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
 		end = start + bvec->bv_offset + bvec->bv_len - 1;
 		len = bvec->bv_len;
 
-		if (++bvec <= bvec_end)
-			prefetchw(&bvec->bv_page->flags);
-
 		mirror = io_bio->mirror_num;
 		if (likely(uptodate && tree->ops &&
 			   tree->ops->readpage_end_io_hook)) {
@@ -2516,7 +2511,7 @@ readpage_ok:
 			extent_start = start;
 			extent_len = end + 1 - start;
 		}
-	} while (bvec <= bvec_end);
+	}
 
 	if (extent_len)
 		endio_readpage_release_extent(tree, extent_start, extent_len,
@@ -2547,7 +2542,6 @@ btrfs_bio_alloc(struct block_device *bdev, u64 first_sector, int nr_vecs,
 	}
 
 	if (bio) {
-		bio->bi_size = 0;
 		bio->bi_bdev = bdev;
 		bio->bi_sector = first_sector;
 		btrfs_bio = btrfs_io_bio(bio);
@@ -3410,20 +3404,18 @@ static void end_extent_buffer_writeback(struct extent_buffer *eb)
 
 static void end_bio_extent_buffer_writepage(struct bio *bio, int err)
 {
-	int uptodate = err == 0;
-	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+	struct bio_vec *bvec;
 	struct extent_buffer *eb;
-	int done;
+	int i, done;
 
-	do {
+	bio_for_each_segment_all(bvec, bio, i) {
 		struct page *page = bvec->bv_page;
 
-		bvec--;
 		eb = (struct extent_buffer *)page->private;
 		BUG_ON(!eb);
 		done = atomic_dec_and_test(&eb->io_pages);
 
-		if (!uptodate || test_bit(EXTENT_BUFFER_IOERR, &eb->bflags)) {
+		if (err || test_bit(EXTENT_BUFFER_IOERR, &eb->bflags)) {
 			set_bit(EXTENT_BUFFER_IOERR, &eb->bflags);
 			ClearPageUptodate(page);
 			SetPageError(page);
@@ -3435,10 +3427,9 @@ static void end_bio_extent_buffer_writepage(struct bio *bio, int err)
 			continue;
 
 		end_extent_buffer_writeback(eb);
-	} while (bvec >= bio->bi_io_vec);
+	}
 
 	bio_put(bio);
-
 }
 
 static int write_one_eb(struct extent_buffer *eb,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f1a7744..d6630dc 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6779,17 +6779,16 @@ unlock_err:
 static void btrfs_endio_direct_read(struct bio *bio, int err)
 {
 	struct btrfs_dio_private *dip = bio->bi_private;
-	struct bio_vec *bvec_end = bio->bi_io_vec + bio->bi_vcnt - 1;
-	struct bio_vec *bvec = bio->bi_io_vec;
+	struct bio_vec *bvec;
 	struct inode *inode = dip->inode;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct bio *dio_bio;
 	u32 *csums = (u32 *)dip->csum;
-	int index = 0;
 	u64 start;
+	int i;
 
 	start = dip->logical_offset;
-	do {
+	bio_for_each_segment_all(bvec, bio, i) {
 		if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
 			struct page *page = bvec->bv_page;
 			char *kaddr;
@@ -6805,18 +6804,16 @@ static void btrfs_endio_direct_read(struct bio *bio, int err)
 			local_irq_restore(flags);
 
 			flush_dcache_page(bvec->bv_page);
-			if (csum != csums[index]) {
+			if (csum != csums[i]) {
 				btrfs_err(root->fs_info, "csum failed ino %llu off %llu csum %u expected csum %u",
 					  btrfs_ino(inode), start, csum,
-					  csums[index]);
+					  csums[i]);
 				err = -EIO;
 			}
 		}
 
 		start += bvec->bv_len;
-		bvec++;
-		index++;
-	} while (bvec <= bvec_end);
+	}
 
 	unlock_extent(&BTRFS_I(inode)->io_tree, dip->logical_offset,
 		      dip->logical_offset + dip->bytes - 1);