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Subject[RFC][PATCH 2/10] I/O context inheritance
From

Every I/O scheduler should get a iocontext from a given bio,
not from the current process.


Signed-off-by: Hirokazu Takahashi <taka@valinux.co.jp>


--- linux-2.6.25.bio0/block/blk-core.c 2008-04-22 15:48:32.000000000 +0900
+++ linux-2.6.25/block/blk-core.c 2008-04-22 16:13:31.000000000 +0900
@@ -600,7 +600,8 @@ static inline void blk_free_request(stru
}

static struct request *
-blk_alloc_request(struct request_queue *q, int rw, int priv, gfp_t gfp_mask)
+blk_alloc_request(struct request_queue *q, int rw, int priv, gfp_t gfp_mask,
+ struct io_context *ioc)
{
struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);

@@ -614,7 +615,7 @@ blk_alloc_request(struct request_queue *
rq->cmd_flags = rw | REQ_ALLOCED;

if (priv) {
- if (unlikely(elv_set_request(q, rq, gfp_mask))) {
+ if (unlikely(elv_set_request(q, rq, gfp_mask, ioc))) {
mempool_free(rq, q->rq.rq_pool);
return NULL;
}
@@ -702,7 +703,7 @@ static struct request *get_request(struc
{
struct request *rq = NULL;
struct request_list *rl = &q->rq;
- struct io_context *ioc = NULL;
+ struct io_context *ioc;
const int rw = rw_flags & 0x01;
int may_queue, priv;

@@ -710,9 +711,12 @@ static struct request *get_request(struc
if (may_queue == ELV_MQUEUE_NO)
goto rq_starved;

+ ioc = bio ? bio->bi_io_context : current->io_context;
+
if (rl->count[rw]+1 >= queue_congestion_on_threshold(q)) {
if (rl->count[rw]+1 >= q->nr_requests) {
- ioc = current_io_context(GFP_ATOMIC, q->node);
+ if (!ioc)
+ ioc = current_io_context(GFP_ATOMIC, q->node);
/*
* The queue will fill after this allocation, so set
* it as full, and mark this process as "batching".
@@ -754,7 +758,7 @@ static struct request *get_request(struc

spin_unlock_irq(q->queue_lock);

- rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
+ rq = blk_alloc_request(q, rw_flags, priv, gfp_mask, ioc);
if (unlikely(!rq)) {
/*
* Allocation failed presumably due to memory. Undo anything
--- linux-2.6.25.bio0/include/linux/elevator.h 2008-04-22 15:48:36.000000000 +0900
+++ linux-2.6.25/include/linux/elevator.h 2008-04-22 15:51:27.000000000 +0900
@@ -22,7 +22,7 @@ typedef struct request *(elevator_reques
typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
typedef int (elevator_may_queue_fn) (struct request_queue *, int);

-typedef int (elevator_set_req_fn) (struct request_queue *, struct request *, gfp_t);
+typedef int (elevator_set_req_fn) (struct request_queue *, struct request *, gfp_t, struct io_context *);
typedef void (elevator_put_req_fn) (struct request *);
typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
@@ -113,7 +113,7 @@ extern int elv_register_queue(struct req
extern void elv_unregister_queue(struct request_queue *q);
extern int elv_may_queue(struct request_queue *, int);
extern void elv_completed_request(struct request_queue *, struct request *);
-extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
+extern int elv_set_request(struct request_queue *, struct request *, gfp_t, struct io_context *);
extern void elv_put_request(struct request_queue *, struct request *);

/*
--- linux-2.6.25.bio0/block/elevator.c 2008-04-22 15:48:32.000000000 +0900
+++ linux-2.6.25/block/elevator.c 2008-04-22 15:51:27.000000000 +0900
@@ -864,12 +864,13 @@ struct request *elv_former_request(struc
return NULL;
}

-int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
+int elv_set_request(struct request_queue *q, struct request *rq,
+ gfp_t gfp_mask, struct io_context *ioc)
{
elevator_t *e = q->elevator;

if (e->ops->elevator_set_req_fn)
- return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
+ return e->ops->elevator_set_req_fn(q, rq, gfp_mask, ioc);

rq->elevator_private = NULL;
return 0;
--- linux-2.6.25.bio0/block/cfq-iosched.c 2008-04-22 15:48:32.000000000 +0900
+++ linux-2.6.25/block/cfq-iosched.c 2008-04-22 17:15:21.000000000 +0900
@@ -1571,14 +1571,16 @@ static int cfq_cic_link(struct cfq_data
* than one device managed by cfq.
*/
static struct cfq_io_context *
-cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
+cfq_get_io_context(struct cfq_data *cfqd, struct io_context *ioc, gfp_t gfp_mask)
{
- struct io_context *ioc = NULL;
struct cfq_io_context *cic;

might_sleep_if(gfp_mask & __GFP_WAIT);

- ioc = get_io_context(gfp_mask, cfqd->queue->node);
+ ioc = ioc_object_link(ioc);
+
+ if (!ioc)
+ ioc = get_io_context(gfp_mask, cfqd->queue->node);
if (!ioc)
return NULL;

@@ -1938,7 +1940,8 @@ static void cfq_put_request(struct reque
* Allocate cfq data structures associated with this request.
*/
static int
-cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
+cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask,
+ struct io_context *ioc)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_io_context *cic;
@@ -1949,7 +1952,7 @@ cfq_set_request(struct request_queue *q,

might_sleep_if(gfp_mask & __GFP_WAIT);

- cic = cfq_get_io_context(cfqd, gfp_mask);
+ cic = cfq_get_io_context(cfqd, ioc, gfp_mask);

spin_lock_irqsave(q->queue_lock, flags);


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