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>

1 files changed, 13 insertions, 22 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index ff43802a7c8..8b5f9e1d1f0 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,