[PATCH 4/4] erofs: add REQ_RAHEAD flag to readahead requests

[Gao Xiang <hsiangkao@redhat.com>]

Let's add REQ_RAHEAD flag so it'd be easier to identify
readahead I/O requests in blktrace.

Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
---
 fs/erofs/data.c  | 2 +-
 fs/erofs/zdata.c | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/data.c b/fs/erofs/data.c
index 459ecb42cbd3..347be146884c 100644
--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -224,7 +224,7 @@ static inline struct bio *erofs_read_raw_page(struct bio *bio,
 		bio_set_dev(bio, sb->s_bdev);
 		bio->bi_iter.bi_sector = (sector_t)blknr <<
 			LOG_SECTORS_PER_BLOCK;
-		bio->bi_opf = REQ_OP_READ;
+		bio->bi_opf = REQ_OP_READ | (ra ? REQ_RAHEAD : 0);
 	}
 
 	err = bio_add_page(bio, page, PAGE_SIZE, 0);
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index bb20f73f10e0..23940edf16ce 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -136,6 +136,7 @@ struct z_erofs_decompress_frontend {
 	struct erofs_map_blocks map;
 
 	unsigned int compressedblock_total;
+	bool readahead;
 
 	/* used for applying cache strategy on the fly */
 	bool backmost;
@@ -1220,6 +1221,8 @@ static void z_erofs_submit_queue(struct super_block *sb,
 					LOG_SECTORS_PER_BLOCK;
 				bio->bi_private = bi_private;
 				bio->bi_opf = REQ_OP_READ;
+				if (f->readahead)
+					bio->bi_opf |= REQ_RAHEAD;
 				++nr_bios;
 			}
 
@@ -1318,6 +1321,7 @@ static void z_erofs_readahead(struct readahead_control *rac)
 
 	trace_erofs_readpages(inode, readahead_index(rac), nr_pages, false);
 
+	f.readahead = true;
 	f.headoffset = readahead_pos(rac);
 
 	while ((page = readahead_page(rac))) {
-- 
2.18.1