[BLOCK] Reimplement elevator switch (cb98fc8b) · Commits · 戴 / test

drivers/block/elevator.c

+35 −43

Original line number	Diff line number	Diff line
		@@ -34,6 +34,7 @@
		#include <linux/slab.h>
		#include <linux/init.h>
		#include <linux/compiler.h>
		#include <linux/delay.h>

		#include <asm/uaccess.h>

		@@ -131,11 +132,7 @@ static int elevator_attach(request_queue_t q, struct elevator_type e,
		eq->ops = &e->ops;
		eq->elevator_type = e;

		INIT_LIST_HEAD(&q->queue_head);
		q->last_merge = NULL;
		q->elevator = eq;
		q->end_sector = 0;
		q->boundary_rq = NULL;

		if (eq->ops->elevator_init_fn)
		ret = eq->ops->elevator_init_fn(q, eq);
		@@ -184,6 +181,12 @@ int elevator_init(request_queue_t q, char name)
		struct elevator_queue *eq;
		int ret = 0;

		INIT_LIST_HEAD(&q->queue_head);
		q->last_merge = NULL;
		q->end_sector = 0;
		q->boundary_rq = NULL;
		q->max_back_kb = 0;

		elevator_setup_default();

		if (!name)
		@@ -336,23 +339,14 @@ void __elv_add_request(request_queue_t q, struct request rq, int where,
		q->end_sector = rq_end_sector(rq);
		q->boundary_rq = rq;
		}
		}
		} else if (!(rq->flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
		where = ELEVATOR_INSERT_BACK;

		if (plug)
		blk_plug_device(q);

		rq->q = q;

		if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))) {
		/*
		* if drain is set, store the request "locally". when the drain
		* is finished, the requests will be handed ordered to the io
		* scheduler
		*/
		list_add_tail(&rq->queuelist, &q->drain_list);
		return;
		}

		switch (where) {
		case ELEVATOR_INSERT_FRONT:
		rq->flags \|= REQ_SOFTBARRIER;
		@@ -659,25 +653,36 @@ EXPORT_SYMBOL_GPL(elv_unregister);
		* switch to new_e io scheduler. be careful not to introduce deadlocks -
		* we don't free the old io scheduler, before we have allocated what we
		* need for the new one. this way we have a chance of going back to the old
		* one, if the new one fails init for some reason. we also do an intermediate
		* switch to noop to ensure safety with stack-allocated requests, since they
		* don't originate from the block layer allocator. noop is safe here, because
		* it never needs to touch the elevator itself for completion events. DRAIN
		* flags will make sure we don't touch it for additions either.
		* one, if the new one fails init for some reason.
		*/
		static void elevator_switch(request_queue_t q, struct elevator_type new_e)
		{
		elevator_t *e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
		struct elevator_type *noop_elevator = NULL;
		elevator_t *old_elevator;
		elevator_t old_elevator, e;

		/*
		* Allocate new elevator
		*/
		e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
		if (!e)
		goto error;

		/*
		* first step, drain requests from the block freelist
		* Turn on BYPASS and drain all requests w/ elevator private data
		*/
		blk_wait_queue_drained(q, 0);
		spin_lock_irq(q->queue_lock);

		set_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);

		while (q->elevator->ops->elevator_dispatch_fn(q, 1))
		;

		while (q->rq.elvpriv) {
		spin_unlock_irq(q->queue_lock);
		msleep(100);
		spin_lock_irq(q->queue_lock);
		}

		spin_unlock_irq(q->queue_lock);

		/*
		* unregister old elevator data
		@@ -685,18 +690,6 @@ static void elevator_switch(request_queue_t q, struct elevator_type new_e)
		elv_unregister_queue(q);
		old_elevator = q->elevator;

		/*
		* next step, switch to noop since it uses no private rq structures
		* and doesn't allocate any memory for anything. then wait for any
		* non-fs requests in-flight
		*/
		noop_elevator = elevator_get("noop");
		spin_lock_irq(q->queue_lock);
		elevator_attach(q, noop_elevator, e);
		spin_unlock_irq(q->queue_lock);

		blk_wait_queue_drained(q, 1);

		/*
		* attach and start new elevator
		*/
		@@ -707,11 +700,10 @@ static void elevator_switch(request_queue_t q, struct elevator_type new_e)
		goto fail_register;

		/*
		* finally exit old elevator and start queue again
		* finally exit old elevator and turn off BYPASS.
		*/
		elevator_exit(old_elevator);
		blk_finish_queue_drain(q);
		elevator_put(noop_elevator);
		clear_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);
		return;

		fail_register:
		@@ -720,13 +712,13 @@ fail_register:
		* one again (along with re-adding the sysfs dir)
		*/
		elevator_exit(e);
		e = NULL;
		fail:
		q->elevator = old_elevator;
		elv_register_queue(q);
		blk_finish_queue_drain(q);
		clear_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);
		kfree(e);
		error:
		if (noop_elevator)
		elevator_put(noop_elevator);
		elevator_put(new_e);
		printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name);
		}

drivers/block/ll_rw_blk.c

+27 −115

Original line number	Diff line number	Diff line
		@@ -263,8 +263,6 @@ void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn)
		blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);

		blk_queue_activity_fn(q, NULL, NULL);

		INIT_LIST_HEAD(&q->drain_list);
		}

		EXPORT_SYMBOL(blk_queue_make_request);
		@@ -1050,6 +1048,7 @@ static char *rq_flags[] = {
		"REQ_STARTED",
		"REQ_DONTPREP",
		"REQ_QUEUED",
		"REQ_ELVPRIV",
		"REQ_PC",
		"REQ_BLOCK_PC",
		"REQ_SENSE",
		@@ -1640,9 +1639,9 @@ static int blk_init_free_list(request_queue_t *q)

		rl->count[READ] = rl->count[WRITE] = 0;
		rl->starved[READ] = rl->starved[WRITE] = 0;
		rl->elvpriv = 0;
		init_waitqueue_head(&rl->wait[READ]);
		init_waitqueue_head(&rl->wait[WRITE]);
		init_waitqueue_head(&rl->drain);

		rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
		mempool_free_slab, request_cachep, q->node);
		@@ -1785,12 +1784,14 @@ EXPORT_SYMBOL(blk_get_queue);

		static inline void blk_free_request(request_queue_t q, struct request rq)
		{
		if (rq->flags & REQ_ELVPRIV)
		elv_put_request(q, rq);
		mempool_free(rq, q->rq.rq_pool);
		}

		static inline struct request *
		blk_alloc_request(request_queue_t q, int rw, struct bio bio, int gfp_mask)
		blk_alloc_request(request_queue_t q, int rw, struct bio bio,
		int priv, int gfp_mask)
		{
		struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);

		@@ -1803,12 +1804,16 @@ blk_alloc_request(request_queue_t q, int rw, struct bio bio, int gfp_mask)
		*/
		rq->flags = rw;

		if (!elv_set_request(q, rq, bio, gfp_mask))
		return rq;

		if (priv) {
		if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) {
		mempool_free(rq, q->rq.rq_pool);
		return NULL;
		}
		rq->flags \|= REQ_ELVPRIV;
		}

		return rq;
		}

		/*
		* ioc_batching returns true if the ioc is a valid batching request and
		@@ -1863,22 +1868,18 @@ static void __freed_request(request_queue_t *q, int rw)
		* A request has just been released. Account for it, update the full and
		* congestion status, wake up any waiters. Called under q->queue_lock.
		*/
		static void freed_request(request_queue_t *q, int rw)
		static void freed_request(request_queue_t *q, int rw, int priv)
		{
		struct request_list *rl = &q->rq;

		rl->count[rw]--;
		if (priv)
		rl->elvpriv--;

		__freed_request(q, rw);

		if (unlikely(rl->starved[rw ^ 1]))
		__freed_request(q, rw ^ 1);

		if (!rl->count[READ] && !rl->count[WRITE]) {
		smp_mb();
		if (unlikely(waitqueue_active(&rl->drain)))
		wake_up(&rl->drain);
		}
		}

		#define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
		@@ -1893,9 +1894,7 @@ static struct request get_request(request_queue_t q, int rw, struct bio *bio,
		struct request *rq = NULL;
		struct request_list *rl = &q->rq;
		struct io_context *ioc = current_io_context(GFP_ATOMIC);

		if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)))
		goto out;
		int priv;

		if (rl->count[rw]+1 >= q->nr_requests) {
		/*
		@@ -1940,9 +1939,14 @@ get_rq:
		rl->starved[rw] = 0;
		if (rl->count[rw] >= queue_congestion_on_threshold(q))
		set_queue_congested(q, rw);

		priv = !test_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);
		if (priv)
		rl->elvpriv++;

		spin_unlock_irq(q->queue_lock);

		rq = blk_alloc_request(q, rw, bio, gfp_mask);
		rq = blk_alloc_request(q, rw, bio, priv, gfp_mask);
		if (!rq) {
		/*
		* Allocation failed presumably due to memory. Undo anything
		@@ -1952,7 +1956,7 @@ get_rq:
		* wait queue, but this is pretty rare.
		*/
		spin_lock_irq(q->queue_lock);
		freed_request(q, rw);
		freed_request(q, rw, priv);

		/*
		* in the very unlikely event that allocation failed and no
		@@ -2470,11 +2474,12 @@ static void __blk_put_request(request_queue_t q, struct request req)
		*/
		if (rl) {
		int rw = rq_data_dir(req);
		int priv = req->flags & REQ_ELVPRIV;

		BUG_ON(!list_empty(&req->queuelist));

		blk_free_request(q, req);
		freed_request(q, rw);
		freed_request(q, rw, priv);
		}
		}

		@@ -2802,97 +2807,6 @@ static inline void blk_partition_remap(struct bio *bio)
		}
		}

		void blk_finish_queue_drain(request_queue_t *q)
		{
		struct request_list *rl = &q->rq;
		struct request *rq;
		int requeued = 0;

		spin_lock_irq(q->queue_lock);
		clear_bit(QUEUE_FLAG_DRAIN, &q->queue_flags);

		while (!list_empty(&q->drain_list)) {
		rq = list_entry_rq(q->drain_list.next);

		list_del_init(&rq->queuelist);
		elv_requeue_request(q, rq);
		requeued++;
		}

		if (requeued)
		q->request_fn(q);

		spin_unlock_irq(q->queue_lock);

		wake_up(&rl->wait[0]);
		wake_up(&rl->wait[1]);
		wake_up(&rl->drain);
		}

		static int wait_drain(request_queue_t q, struct request_list rl, int dispatch)
		{
		int wait = rl->count[READ] + rl->count[WRITE];

		if (dispatch)
		wait += !list_empty(&q->queue_head);

		return wait;
		}

		/*
		* We rely on the fact that only requests allocated through blk_alloc_request()
		* have io scheduler private data structures associated with them. Any other
		* type of request (allocated on stack or through kmalloc()) should not go
		* to the io scheduler core, but be attached to the queue head instead.
		*/
		void blk_wait_queue_drained(request_queue_t *q, int wait_dispatch)
		{
		struct request_list *rl = &q->rq;
		DEFINE_WAIT(wait);

		spin_lock_irq(q->queue_lock);
		set_bit(QUEUE_FLAG_DRAIN, &q->queue_flags);

		while (wait_drain(q, rl, wait_dispatch)) {
		prepare_to_wait(&rl->drain, &wait, TASK_UNINTERRUPTIBLE);

		if (wait_drain(q, rl, wait_dispatch)) {
		__generic_unplug_device(q);
		spin_unlock_irq(q->queue_lock);
		io_schedule();
		spin_lock_irq(q->queue_lock);
		}

		finish_wait(&rl->drain, &wait);
		}

		spin_unlock_irq(q->queue_lock);
		}

		/*
		* block waiting for the io scheduler being started again.
		*/
		static inline void block_wait_queue_running(request_queue_t *q)
		{
		DEFINE_WAIT(wait);

		while (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))) {
		struct request_list *rl = &q->rq;

		prepare_to_wait_exclusive(&rl->drain, &wait,
		TASK_UNINTERRUPTIBLE);

		/*
		* re-check the condition. avoids using prepare_to_wait()
		* in the fast path (queue is running)
		*/
		if (test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))
		io_schedule();

		finish_wait(&rl->drain, &wait);
		}
		}

		static void handle_bad_sector(struct bio *bio)
		{
		char b[BDEVNAME_SIZE];
		@@ -2988,8 +2902,6 @@ end_io:
		if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
		goto end_io;

		block_wait_queue_running(q);

		/*
		* If this device has partitions, remap block n
		* of partition p to block n+start(p) of the disk.

include/linux/blkdev.h

+4 −6

Original line number	Diff line number	Diff line
		@@ -107,9 +107,9 @@ typedef void (rq_end_io_fn)(struct request *);
		struct request_list {
		int count[2];
		int starved[2];
		int elvpriv;
		mempool_t *rq_pool;
		wait_queue_head_t wait[2];
		wait_queue_head_t drain;
		};

		#define BLK_MAX_CDB 16
		@@ -211,6 +211,7 @@ enum rq_flag_bits {
		__REQ_STARTED, /* drive already may have started this one */
		__REQ_DONTPREP, /* don't call prep for this one */
		__REQ_QUEUED, /* uses queueing */
		__REQ_ELVPRIV, /* elevator private data attached */
		/*
		* for ATA/ATAPI devices
		*/
		@@ -244,6 +245,7 @@ enum rq_flag_bits {
		#define REQ_STARTED (1 << __REQ_STARTED)
		#define REQ_DONTPREP (1 << __REQ_DONTPREP)
		#define REQ_QUEUED (1 << __REQ_QUEUED)
		#define REQ_ELVPRIV (1 << __REQ_ELVPRIV)
		#define REQ_PC (1 << __REQ_PC)
		#define REQ_BLOCK_PC (1 << __REQ_BLOCK_PC)
		#define REQ_SENSE (1 << __REQ_SENSE)
		@@ -413,8 +415,6 @@ struct request_queue
		unsigned int sg_reserved_size;
		int node;

		struct list_head drain_list;

		/*
		* reserved for flush operations
		*/
		@@ -442,7 +442,7 @@ enum {
		#define QUEUE_FLAG_DEAD 5 /* queue being torn down */
		#define QUEUE_FLAG_REENTER 6 /* Re-entrancy avoidance */
		#define QUEUE_FLAG_PLUGGED 7 /* queue is plugged */
		#define QUEUE_FLAG_DRAIN 8 /* draining queue for sched switch */
		#define QUEUE_FLAG_BYPASS 8 /* don't use elevator, just do FIFO */
		#define QUEUE_FLAG_FLUSH 9 /* doing barrier flush sequence */

		#define blk_queue_plugged(q) test_bit(QUEUE_FLAG_PLUGGED, &(q)->queue_flags)
		@@ -668,8 +668,6 @@ extern void blk_dump_rq_flags(struct request , char );
		extern void generic_unplug_device(request_queue_t *);
		extern void __generic_unplug_device(request_queue_t *);
		extern long nr_blockdev_pages(void);
		extern void blk_wait_queue_drained(request_queue_t *, int);
		extern void blk_finish_queue_drain(request_queue_t *);

		int blk_get_queue(request_queue_t *);
		request_queue_t *blk_alloc_queue(int gfp_mask);

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