[PATCH] Allow file systems to differentiate between data and meta reads

We can use this information for making more intelligent priority
decisions, and it will also be useful for blktrace.
Signed-off-by: Jens Axboe <axboe@suse.de>

block/ll_rw_blk.c

@@ -2884,6 +2884,8 @@ static void init_request_from_bio(struct request *req, struct bio *bio)
 
 	if (bio_sync(bio))
 		req->cmd_flags |= REQ_RW_SYNC;
+	if (bio_rw_meta(bio))
+		req->cmd_flags |= REQ_RW_META;
 
 	req->errors = 0;
 	req->hard_sector = req->sector = bio->bi_sector;

include/linux/bio.h

@@ -148,6 +148,7 @@ struct bio {
 #define BIO_RW_BARRIER	2
 #define BIO_RW_FAILFAST	3
 #define BIO_RW_SYNC	4
+#define BIO_RW_META	5
 
 /*
  * upper 16 bits of bi_rw define the io priority of this bio
@@ -178,6 +179,7 @@ struct bio {
 #define bio_sync(bio)		((bio)->bi_rw & (1 << BIO_RW_SYNC))
 #define bio_failfast(bio)	((bio)->bi_rw & (1 << BIO_RW_FAILFAST))
 #define bio_rw_ahead(bio)	((bio)->bi_rw & (1 << BIO_RW_AHEAD))
+#define bio_rw_meta(bio)	((bio)->bi_rw & (1 << BIO_RW_META))
 
 /*
  * will die

include/linux/blkdev.h

@@ -180,6 +180,7 @@ enum rq_flag_bits {
 	__REQ_ORDERED_COLOR,	/* is before or after barrier */
 	__REQ_RW_SYNC,		/* request is sync (O_DIRECT) */
 	__REQ_ALLOCED,		/* request came from our alloc pool */
+	__REQ_RW_META,		/* metadata io request */
 	__REQ_NR_BITS,		/* stops here */
 };
 
@@ -200,6 +201,7 @@ enum rq_flag_bits {
 #define REQ_ORDERED_COLOR	(1 << __REQ_ORDERED_COLOR)
 #define REQ_RW_SYNC	(1 << __REQ_RW_SYNC)
 #define REQ_ALLOCED	(1 << __REQ_ALLOCED)
+#define REQ_RW_META	(1 << __REQ_RW_META)
 
 #define BLK_MAX_CDB	16
 
@@ -543,6 +545,7 @@ enum {
  * We regard a request as sync, if it's a READ or a SYNC write.
  */
 #define rq_is_sync(rq)		(rq_data_dir((rq)) == READ || (rq)->cmd_flags & REQ_RW_SYNC)
+#define rq_is_meta(rq)		((rq)->cmd_flags & REQ_RW_META)
 
 static inline int blk_queue_full(struct request_queue *q, int rw)
 {

include/linux/fs.h

@@ -80,6 +80,7 @@ extern int dir_notify_enable;
 #define READA 2		/* read-ahead  - don't block if no resources */
 #define SWRITE 3	/* for ll_rw_block() - wait for buffer lock */
 #define READ_SYNC	(READ | (1 << BIO_RW_SYNC))
+#define READ_META	(READ | (1 << BIO_RW_META))
 #define WRITE_SYNC	(WRITE | (1 << BIO_RW_SYNC))
 #define WRITE_BARRIER	((1 << BIO_RW) | (1 << BIO_RW_BARRIER))