[PATCH 2/4] block: use the same failfast bits for bio and request
From: Tejun Heo
Date: Fri Jul 03 2009 - 04:49:48 EST
bio and request use the same set of failfast bits. This patch makes
the following changes to simplify things.
* enumify BIO_RW* bits and reorder bits such that BIOS_RW_FAILFAST_*
bits coincide with __REQ_FAILFAST_* bits.
* The above pushes BIO_RW_AHEAD out of sync with __REQ_FAILFAST_DEV
but the matching is useless anyway. init_request_from_bio() is
responsible for setting FAILFAST bits on FS requests and non-FS
requests never use BIO_RW_AHEAD. Drop the code and comment from
blk_rq_bio_prep().
* Define REQ_FAILFAST_MASK which is OR of all FAILFAST bits and
simplify FAILFAST flags handling in init_request_from_bio().
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
---
block/blk-core.c | 19 +++++++------------
include/linux/bio.h | 43 +++++++++++++++++++++++--------------------
include/linux/blkdev.h | 4 ++++
3 files changed, 34 insertions(+), 32 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 8f4b9e0..cd3b265 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1119,17 +1119,13 @@ void init_request_from_bio(struct request *req, struct bio *bio)
req->cmd_type = REQ_TYPE_FS;
/*
- * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
+ * Inherit FAILFAST from bio (for read-ahead, and explicit
+ * FAILFAST). FAILFAST flags are identical for req and bio.
*/
if (bio_rw_ahead(bio))
- req->cmd_flags |= (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
- REQ_FAILFAST_DRIVER);
- if (bio_failfast_dev(bio))
- req->cmd_flags |= REQ_FAILFAST_DEV;
- if (bio_failfast_transport(bio))
- req->cmd_flags |= REQ_FAILFAST_TRANSPORT;
- if (bio_failfast_driver(bio))
- req->cmd_flags |= REQ_FAILFAST_DRIVER;
+ req->cmd_flags |= REQ_FAILFAST_MASK;
+ else
+ req->cmd_flags |= bio->bi_rw & REQ_FAILFAST_MASK;
if (unlikely(bio_discard(bio))) {
req->cmd_flags |= REQ_DISCARD;
@@ -2247,9 +2243,8 @@ EXPORT_SYMBOL_GPL(__blk_end_request_cur);
void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
struct bio *bio)
{
- /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw, and
- we want BIO_RW_AHEAD (bit 1) to imply REQ_FAILFAST (bit 1). */
- rq->cmd_flags |= (bio->bi_rw & 3);
+ /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
+ rq->cmd_flags |= bio->bi_rw & REQ_RW;
if (bio_has_data(bio)) {
rq->nr_phys_segments = bio_phys_segments(q, bio);
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 2892b71..a299ed3 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -142,37 +142,40 @@ struct bio {
*
* bit 0 -- data direction
* If not set, bio is a read from device. If set, it's a write to device.
- * bit 1 -- rw-ahead when set
- * bit 2 -- barrier
+ * bit 1 -- fail fast device errors
+ * bit 2 -- fail fast transport errors
+ * bit 3 -- fail fast driver errors
+ * bit 4 -- rw-ahead when set
+ * bit 5 -- barrier
* Insert a serialization point in the IO queue, forcing previously
* submitted IO to be completed before this one is issued.
- * bit 3 -- synchronous I/O hint.
- * bit 4 -- Unplug the device immediately after submitting this bio.
- * bit 5 -- metadata request
+ * bit 6 -- synchronous I/O hint.
+ * bit 7 -- Unplug the device immediately after submitting this bio.
+ * bit 8 -- metadata request
* Used for tracing to differentiate metadata and data IO. May also
* get some preferential treatment in the IO scheduler
- * bit 6 -- discard sectors
+ * bit 9 -- discard sectors
* Informs the lower level device that this range of sectors is no longer
* used by the file system and may thus be freed by the device. Used
* for flash based storage.
- * bit 7 -- fail fast device errors
- * bit 8 -- fail fast transport errors
- * bit 9 -- fail fast driver errors
* Don't want driver retries for any fast fail whatever the reason.
* bit 10 -- Tell the IO scheduler not to wait for more requests after this
one has been submitted, even if it is a SYNC request.
*/
-#define BIO_RW 0 /* Must match RW in req flags (blkdev.h) */
-#define BIO_RW_AHEAD 1 /* Must match FAILFAST in req flags */
-#define BIO_RW_BARRIER 2
-#define BIO_RW_SYNCIO 3
-#define BIO_RW_UNPLUG 4
-#define BIO_RW_META 5
-#define BIO_RW_DISCARD 6
-#define BIO_RW_FAILFAST_DEV 7
-#define BIO_RW_FAILFAST_TRANSPORT 8
-#define BIO_RW_FAILFAST_DRIVER 9
-#define BIO_RW_NOIDLE 10
+enum bio_rw_flags {
+ BIO_RW,
+ BIO_RW_FAILFAST_DEV,
+ BIO_RW_FAILFAST_TRANSPORT,
+ BIO_RW_FAILFAST_DRIVER,
+ /* above flags must match REQ_* */
+ BIO_RW_AHEAD,
+ BIO_RW_BARRIER,
+ BIO_RW_SYNCIO,
+ BIO_RW_UNPLUG,
+ BIO_RW_META,
+ BIO_RW_DISCARD,
+ BIO_RW_NOIDLE,
+};
#define bio_rw_flagged(bio, flag) ((bio)->bi_rw & (1 << (flag)))
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 49ae079..a0e5ce1 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -98,6 +98,7 @@ enum rq_flag_bits {
__REQ_FAILFAST_DEV, /* no driver retries of device errors */
__REQ_FAILFAST_TRANSPORT, /* no driver retries of transport errors */
__REQ_FAILFAST_DRIVER, /* no driver retries of driver errors */
+ /* above flags must match BIO_RW_* */
__REQ_DISCARD, /* request to discard sectors */
__REQ_SORTED, /* elevator knows about this request */
__REQ_SOFTBARRIER, /* may not be passed by ioscheduler */
@@ -148,6 +149,9 @@ enum rq_flag_bits {
#define REQ_NOIDLE (1 << __REQ_NOIDLE)
#define REQ_IO_STAT (1 << __REQ_IO_STAT)
+#define REQ_FAILFAST_MASK (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | \
+ REQ_FAILFAST_DRIVER)
+
#define BLK_MAX_CDB 16
/*
--
1.6.0.2
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