[PATCH] Kill PF_SYNCWRITE flag
A process flag to indicate whether we are doing sync io is incredibly
ugly. It also causes performance problems when one does a lot of async
io and then proceeds to sync it. Part of the io will go out as async,
and the other part as sync. This causes a disconnect between the
previously submitted io and the synced io. For io schedulers such as CFQ,
this will cause us lost merges and suboptimal behaviour in scheduling.
Remove PF_SYNCWRITE completely from the fsync/msync paths, and let
the O_DIRECT path just directly indicate that the writes are sync
by using WRITE_SYNC instead.
Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/block/as-iosched.c b/block/as-iosched.c
index 9b13d72..56c99fa 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -1339,7 +1339,7 @@
arq->state = AS_RQ_NEW;
if (rq_data_dir(arq->request) == READ
- || current->flags&PF_SYNCWRITE)
+ || (arq->request->flags & REQ_RW_SYNC))
arq->is_sync = 1;
else
arq->is_sync = 0;
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index c88f161d..4c4e9cc 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -277,8 +277,6 @@
static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
-#define process_sync(tsk) ((tsk)->flags & PF_SYNCWRITE)
-
/*
* lots of deadline iosched dupes, can be abstracted later...
*/
@@ -334,7 +332,7 @@
static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
{
- if (rw == READ || process_sync(task))
+ if (rw == READ || rw == WRITE_SYNC)
return task->pid;
return CFQ_KEY_ASYNC;
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 17c42dd..2270bb4 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -2827,6 +2827,9 @@
if (unlikely(bio_barrier(bio)))
req->flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
+ if (bio_sync(bio))
+ req->flags |= REQ_RW_SYNC;
+
req->errors = 0;
req->hard_sector = req->sector = bio->bi_sector;
req->hard_nr_sectors = req->nr_sectors = bio_sectors(bio);