[PATCH] Propagate down request sync flag

We need to do this, otherwise the io schedulers don't get access to the
sync flag. Then they cannot tell the difference between a regular write
and an O_DIRECT write, which can cause a performance loss.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 78c6b312bd30..533a2938ffd6 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -219,9 +219,12 @@ static int cfq_queue_empty(request_queue_t *q)
         return !cfqd->busy_queues;
 }
 
-static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
+static inline pid_t cfq_queue_pid(struct task_struct *task, int rw, int is_sync)
 {
-        if (rw == READ || rw == WRITE_SYNC)
+        /*
+         * Use the per-process queue, for read requests and syncronous writes
+         */
+        if (!(rw & REQ_RW) || is_sync)
                 return task->pid;
 
         return CFQ_KEY_ASYNC;
@@ -473,7 +476,7 @@ static struct request *
 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
 {
         struct task_struct *tsk = current;
-        pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio));
+        pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio), bio_sync(bio));
         struct cfq_queue *cfqq;
 
         cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
@@ -1748,6 +1751,9 @@ static int cfq_may_queue(request_queue_t *q, int rw)
         struct cfq_data *cfqd = q->elevator->elevator_data;
         struct task_struct *tsk = current;
         struct cfq_queue *cfqq;
+        unsigned int key;
+
+        key = cfq_queue_pid(tsk, rw, rw & REQ_RW_SYNC);
 
         /*
          * don't force setup of a queue from here, as a call to may_queue
@@ -1755,7 +1761,7 @@ static int cfq_may_queue(request_queue_t *q, int rw)
          * so just lookup a possibly existing queue, or return 'may queue'
          * if that fails
          */
-        cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio);
+        cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
         if (cfqq) {
                 cfq_init_prio_data(cfqq);
                 cfq_prio_boost(cfqq);
@@ -1798,10 +1804,10 @@ cfq_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
         struct task_struct *tsk = current;
         struct cfq_io_context *cic;
         const int rw = rq_data_dir(rq);
-        pid_t key = cfq_queue_pid(tsk, rw);
+        const int is_sync = rq_is_sync(rq);
+        pid_t key = cfq_queue_pid(tsk, rw, is_sync);
         struct cfq_queue *cfqq;
         unsigned long flags;
-        int is_sync = key != CFQ_KEY_ASYNC;
 
         might_sleep_if(gfp_mask & __GFP_WAIT);