[PATCH 2/4] mpage: mpage_readpages() should submit IO as read-ahead

[Jens Axboe <axboe@kernel.dk>]

a_ops->readpages() is only ever used for read-ahead, yet we don't
flag the IO being submitted as such. Fix that up. Any file system
that uses mpage_readpages() as it's ->readpages() implementation
will now get this right.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/mpage.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/fs/mpage.c b/fs/mpage.c
index 0ecac5c410f4..a6344996f924 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -142,6 +142,7 @@ struct mpage_readpage_args {
 	unsigned long first_logical_block;
 	get_block_t *get_block;
 	gfp_t gfp;
+	bool is_readahead;
 };
 
 /*
@@ -170,6 +171,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
 	struct block_device *bdev = NULL;
 	int length;
 	int fully_mapped = 1;
+	int op_flags = args->is_readahead ? REQ_RAHEAD : 0;
 	unsigned nblocks;
 	unsigned relative_block;
 
@@ -283,7 +285,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
 	 * This page will go to BIO.  Do we need to send this BIO off first?
 	 */
 	if (args->bio && (args->last_block_in_bio != blocks[0] - 1))
-		args->bio = mpage_bio_submit(REQ_OP_READ, 0, args->bio);
+		args->bio = mpage_bio_submit(REQ_OP_READ, op_flags, args->bio);
 
 alloc_new:
 	if (args->bio == NULL) {
@@ -300,7 +302,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
 
 	length = first_hole << blkbits;
 	if (bio_add_page(args->bio, page, length, 0) < length) {
-		args->bio = mpage_bio_submit(REQ_OP_READ, 0, args->bio);
+		args->bio = mpage_bio_submit(REQ_OP_READ, op_flags, args->bio);
 		goto alloc_new;
 	}
 
@@ -308,7 +310,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
 	nblocks = map_bh->b_size >> blkbits;
 	if ((buffer_boundary(map_bh) && relative_block == nblocks) ||
 	    (first_hole != blocks_per_page))
-		args->bio = mpage_bio_submit(REQ_OP_READ, 0, args->bio);
+		args->bio = mpage_bio_submit(REQ_OP_READ, op_flags, args->bio);
 	else
 		args->last_block_in_bio = blocks[blocks_per_page - 1];
 out:
@@ -316,7 +318,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
 
 confused:
 	if (args->bio)
-		args->bio = mpage_bio_submit(REQ_OP_READ, 0, args->bio);
+		args->bio = mpage_bio_submit(REQ_OP_READ, op_flags, args->bio);
 	if (!PageUptodate(page))
 	        block_read_full_page(page, args->get_block);
 	else
@@ -375,6 +377,7 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages,
 	struct mpage_readpage_args args = {
 		.get_block = get_block,
 		.gfp = readahead_gfp_mask(mapping),
+		.is_readahead = true,
 	};
 	unsigned page_idx;
 
@@ -394,7 +397,7 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages,
 	}
 	BUG_ON(!list_empty(pages));
 	if (args.bio)
-		mpage_bio_submit(REQ_OP_READ, 0, args.bio);
+		mpage_bio_submit(REQ_OP_READ, REQ_RAHEAD, args.bio);
 	return 0;
 }
 EXPORT_SYMBOL(mpage_readpages);
-- 
2.7.4