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-rw-r--r--block/as-iosched.c1985
1 files changed, 1985 insertions, 0 deletions
diff --git a/block/as-iosched.c b/block/as-iosched.c
new file mode 100644
index 0000000..c6744ff
--- /dev/null
+++ b/block/as-iosched.c
@@ -0,0 +1,1985 @@
+/*
+ * linux/drivers/block/as-iosched.c
+ *
+ * Anticipatory & deadline i/o scheduler.
+ *
+ * Copyright (C) 2002 Jens Axboe <axboe@suse.de>
+ * Nick Piggin <piggin@cyberone.com.au>
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/compiler.h>
+#include <linux/hash.h>
+#include <linux/rbtree.h>
+#include <linux/interrupt.h>
+
+#define REQ_SYNC 1
+#define REQ_ASYNC 0
+
+/*
+ * See Documentation/block/as-iosched.txt
+ */
+
+/*
+ * max time before a read is submitted.
+ */
+#define default_read_expire (HZ / 8)
+
+/*
+ * ditto for writes, these limits are not hard, even
+ * if the disk is capable of satisfying them.
+ */
+#define default_write_expire (HZ / 4)
+
+/*
+ * read_batch_expire describes how long we will allow a stream of reads to
+ * persist before looking to see whether it is time to switch over to writes.
+ */
+#define default_read_batch_expire (HZ / 2)
+
+/*
+ * write_batch_expire describes how long we want a stream of writes to run for.
+ * This is not a hard limit, but a target we set for the auto-tuning thingy.
+ * See, the problem is: we can send a lot of writes to disk cache / TCQ in
+ * a short amount of time...
+ */
+#define default_write_batch_expire (HZ / 8)
+
+/*
+ * max time we may wait to anticipate a read (default around 6ms)
+ */
+#define default_antic_expire ((HZ / 150) ? HZ / 150 : 1)
+
+/*
+ * Keep track of up to 20ms thinktimes. We can go as big as we like here,
+ * however huge values tend to interfere and not decay fast enough. A program
+ * might be in a non-io phase of operation. Waiting on user input for example,
+ * or doing a lengthy computation. A small penalty can be justified there, and
+ * will still catch out those processes that constantly have large thinktimes.
+ */
+#define MAX_THINKTIME (HZ/50UL)
+
+/* Bits in as_io_context.state */
+enum as_io_states {
+ AS_TASK_RUNNING=0, /* Process has not exitted */
+ AS_TASK_IOSTARTED, /* Process has started some IO */
+ AS_TASK_IORUNNING, /* Process has completed some IO */
+};
+
+enum anticipation_status {
+ ANTIC_OFF=0, /* Not anticipating (normal operation) */
+ ANTIC_WAIT_REQ, /* The last read has not yet completed */
+ ANTIC_WAIT_NEXT, /* Currently anticipating a request vs
+ last read (which has completed) */
+ ANTIC_FINISHED, /* Anticipating but have found a candidate
+ * or timed out */
+};
+
+struct as_data {
+ /*
+ * run time data
+ */
+
+ struct request_queue *q; /* the "owner" queue */
+
+ /*
+ * requests (as_rq s) are present on both sort_list and fifo_list
+ */
+ struct rb_root sort_list[2];
+ struct list_head fifo_list[2];
+
+ struct as_rq *next_arq[2]; /* next in sort order */
+ sector_t last_sector[2]; /* last REQ_SYNC & REQ_ASYNC sectors */
+ struct list_head *hash; /* request hash */
+
+ unsigned long exit_prob; /* probability a task will exit while
+ being waited on */
+ unsigned long new_ttime_total; /* mean thinktime on new proc */
+ unsigned long new_ttime_mean;
+ u64 new_seek_total; /* mean seek on new proc */
+ sector_t new_seek_mean;
+
+ unsigned long current_batch_expires;
+ unsigned long last_check_fifo[2];
+ int changed_batch; /* 1: waiting for old batch to end */
+ int new_batch; /* 1: waiting on first read complete */
+ int batch_data_dir; /* current batch REQ_SYNC / REQ_ASYNC */
+ int write_batch_count; /* max # of reqs in a write batch */
+ int current_write_count; /* how many requests left this batch */
+ int write_batch_idled; /* has the write batch gone idle? */
+ mempool_t *arq_pool;
+
+ enum anticipation_status antic_status;
+ unsigned long antic_start; /* jiffies: when it started */
+ struct timer_list antic_timer; /* anticipatory scheduling timer */
+ struct work_struct antic_work; /* Deferred unplugging */
+ struct io_context *io_context; /* Identify the expected process */
+ int ioc_finished; /* IO associated with io_context is finished */
+ int nr_dispatched;
+
+ /*
+ * settings that change how the i/o scheduler behaves
+ */
+ unsigned long fifo_expire[2];
+ unsigned long batch_expire[2];
+ unsigned long antic_expire;
+};
+
+#define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo)
+
+/*
+ * per-request data.
+ */
+enum arq_state {
+ AS_RQ_NEW=0, /* New - not referenced and not on any lists */
+ AS_RQ_QUEUED, /* In the request queue. It belongs to the
+ scheduler */
+ AS_RQ_DISPATCHED, /* On the dispatch list. It belongs to the
+ driver now */
+ AS_RQ_PRESCHED, /* Debug poisoning for requests being used */
+ AS_RQ_REMOVED,
+ AS_RQ_MERGED,
+ AS_RQ_POSTSCHED, /* when they shouldn't be */
+};
+
+struct as_rq {
+ /*
+ * rbtree index, key is the starting offset
+ */
+ struct rb_node rb_node;
+ sector_t rb_key;
+
+ struct request *request;
+
+ struct io_context *io_context; /* The submitting task */
+
+ /*
+ * request hash, key is the ending offset (for back merge lookup)
+ */
+ struct list_head hash;
+ unsigned int on_hash;
+
+ /*
+ * expire fifo
+ */
+ struct list_head fifo;
+ unsigned long expires;
+
+ unsigned int is_sync;
+ enum arq_state state;
+};
+
+#define RQ_DATA(rq) ((struct as_rq *) (rq)->elevator_private)
+
+static kmem_cache_t *arq_pool;
+
+/*
+ * IO Context helper functions
+ */
+
+/* Called to deallocate the as_io_context */
+static void free_as_io_context(struct as_io_context *aic)
+{
+ kfree(aic);
+}
+
+/* Called when the task exits */
+static void exit_as_io_context(struct as_io_context *aic)
+{
+ WARN_ON(!test_bit(AS_TASK_RUNNING, &aic->state));
+ clear_bit(AS_TASK_RUNNING, &aic->state);
+}
+
+static struct as_io_context *alloc_as_io_context(void)
+{
+ struct as_io_context *ret;
+
+ ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
+ if (ret) {
+ ret->dtor = free_as_io_context;
+ ret->exit = exit_as_io_context;
+ ret->state = 1 << AS_TASK_RUNNING;
+ atomic_set(&ret->nr_queued, 0);
+ atomic_set(&ret->nr_dispatched, 0);
+ spin_lock_init(&ret->lock);
+ ret->ttime_total = 0;
+ ret->ttime_samples = 0;
+ ret->ttime_mean = 0;
+ ret->seek_total = 0;
+ ret->seek_samples = 0;
+ ret->seek_mean = 0;
+ }
+
+ return ret;
+}
+
+/*
+ * If the current task has no AS IO context then create one and initialise it.
+ * Then take a ref on the task's io context and return it.
+ */
+static struct io_context *as_get_io_context(void)
+{
+ struct io_context *ioc = get_io_context(GFP_ATOMIC);
+ if (ioc && !ioc->aic) {
+ ioc->aic = alloc_as_io_context();
+ if (!ioc->aic) {
+ put_io_context(ioc);
+ ioc = NULL;
+ }
+ }
+ return ioc;
+}
+
+static void as_put_io_context(struct as_rq *arq)
+{
+ struct as_io_context *aic;
+
+ if (unlikely(!arq->io_context))
+ return;
+
+ aic = arq->io_context->aic;
+
+ if (arq->is_sync == REQ_SYNC && aic) {
+ spin_lock(&aic->lock);
+ set_bit(AS_TASK_IORUNNING, &aic->state);
+ aic->last_end_request = jiffies;
+ spin_unlock(&aic->lock);
+ }
+
+ put_io_context(arq->io_context);
+}
+
+/*
+ * the back merge hash support functions
+ */
+static const int as_hash_shift = 6;
+#define AS_HASH_BLOCK(sec) ((sec) >> 3)
+#define AS_HASH_FN(sec) (hash_long(AS_HASH_BLOCK((sec)), as_hash_shift))
+#define AS_HASH_ENTRIES (1 << as_hash_shift)
+#define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
+#define list_entry_hash(ptr) list_entry((ptr), struct as_rq, hash)
+
+static inline void __as_del_arq_hash(struct as_rq *arq)
+{
+ arq->on_hash = 0;
+ list_del_init(&arq->hash);
+}
+
+static inline void as_del_arq_hash(struct as_rq *arq)
+{
+ if (arq->on_hash)
+ __as_del_arq_hash(arq);
+}
+
+static void as_add_arq_hash(struct as_data *ad, struct as_rq *arq)
+{
+ struct request *rq = arq->request;
+
+ BUG_ON(arq->on_hash);
+
+ arq->on_hash = 1;
+ list_add(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]);
+}
+
+/*
+ * move hot entry to front of chain
+ */
+static inline void as_hot_arq_hash(struct as_data *ad, struct as_rq *arq)
+{
+ struct request *rq = arq->request;
+ struct list_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))];
+
+ if (!arq->on_hash) {
+ WARN_ON(1);
+ return;
+ }
+
+ if (arq->hash.prev != head) {
+ list_del(&arq->hash);
+ list_add(&arq->hash, head);
+ }
+}
+
+static struct request *as_find_arq_hash(struct as_data *ad, sector_t offset)
+{
+ struct list_head *hash_list = &ad->hash[AS_HASH_FN(offset)];
+ struct list_head *entry, *next = hash_list->next;
+
+ while ((entry = next) != hash_list) {
+ struct as_rq *arq = list_entry_hash(entry);
+ struct request *__rq = arq->request;
+
+ next = entry->next;
+
+ BUG_ON(!arq->on_hash);
+
+ if (!rq_mergeable(__rq)) {
+ as_del_arq_hash(arq);
+ continue;
+ }
+
+ if (rq_hash_key(__rq) == offset)
+ return __rq;
+ }
+
+ return NULL;
+}
+
+/*
+ * rb tree support functions
+ */
+#define RB_NONE (2)
+#define RB_EMPTY(root) ((root)->rb_node == NULL)
+#define ON_RB(node) ((node)->rb_color != RB_NONE)
+#define RB_CLEAR(node) ((node)->rb_color = RB_NONE)
+#define rb_entry_arq(node) rb_entry((node), struct as_rq, rb_node)
+#define ARQ_RB_ROOT(ad, arq) (&(ad)->sort_list[(arq)->is_sync])
+#define rq_rb_key(rq) (rq)->sector
+
+/*
+ * as_find_first_arq finds the first (lowest sector numbered) request
+ * for the specified data_dir. Used to sweep back to the start of the disk
+ * (1-way elevator) after we process the last (highest sector) request.
+ */
+static struct as_rq *as_find_first_arq(struct as_data *ad, int data_dir)
+{
+ struct rb_node *n = ad->sort_list[data_dir].rb_node;
+
+ if (n == NULL)
+ return NULL;
+
+ for (;;) {
+ if (n->rb_left == NULL)
+ return rb_entry_arq(n);
+
+ n = n->rb_left;
+ }
+}
+
+/*
+ * Add the request to the rb tree if it is unique. If there is an alias (an
+ * existing request against the same sector), which can happen when using
+ * direct IO, then return the alias.
+ */
+static struct as_rq *as_add_arq_rb(struct as_data *ad, struct as_rq *arq)
+{
+ struct rb_node **p = &ARQ_RB_ROOT(ad, arq)->rb_node;
+ struct rb_node *parent = NULL;
+ struct as_rq *__arq;
+ struct request *rq = arq->request;
+
+ arq->rb_key = rq_rb_key(rq);
+
+ while (*p) {
+ parent = *p;
+ __arq = rb_entry_arq(parent);
+
+ if (arq->rb_key < __arq->rb_key)
+ p = &(*p)->rb_left;
+ else if (arq->rb_key > __arq->rb_key)
+ p = &(*p)->rb_right;
+ else
+ return __arq;
+ }
+
+ rb_link_node(&arq->rb_node, parent, p);
+ rb_insert_color(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
+
+ return NULL;
+}
+
+static inline void as_del_arq_rb(struct as_data *ad, struct as_rq *arq)
+{
+ if (!ON_RB(&arq->rb_node)) {
+ WARN_ON(1);
+ return;
+ }
+
+ rb_erase(&arq->rb_node, ARQ_RB_ROOT(ad, arq));
+ RB_CLEAR(&arq->rb_node);
+}
+
+static struct request *
+as_find_arq_rb(struct as_data *ad, sector_t sector, int data_dir)
+{
+ struct rb_node *n = ad->sort_list[data_dir].rb_node;
+ struct as_rq *arq;
+
+ while (n) {
+ arq = rb_entry_arq(n);
+
+ if (sector < arq->rb_key)
+ n = n->rb_left;
+ else if (sector > arq->rb_key)
+ n = n->rb_right;
+ else
+ return arq->request;
+ }
+
+ return NULL;
+}
+
+/*
+ * IO Scheduler proper
+ */
+
+#define MAXBACK (1024 * 1024) /*
+ * Maximum distance the disk will go backward
+ * for a request.
+ */
+
+#define BACK_PENALTY 2
+
+/*
+ * as_choose_req selects the preferred one of two requests of the same data_dir
+ * ignoring time - eg. timeouts, which is the job of as_dispatch_request
+ */
+static struct as_rq *
+as_choose_req(struct as_data *ad, struct as_rq *arq1, struct as_rq *arq2)
+{
+ int data_dir;
+ sector_t last, s1, s2, d1, d2;
+ int r1_wrap=0, r2_wrap=0; /* requests are behind the disk head */
+ const sector_t maxback = MAXBACK;
+
+ if (arq1 == NULL || arq1 == arq2)
+ return arq2;
+ if (arq2 == NULL)
+ return arq1;
+
+ data_dir = arq1->is_sync;
+
+ last = ad->last_sector[data_dir];
+ s1 = arq1->request->sector;
+ s2 = arq2->request->sector;
+
+ BUG_ON(data_dir != arq2->is_sync);
+
+ /*
+ * Strict one way elevator _except_ in the case where we allow
+ * short backward seeks which are biased as twice the cost of a
+ * similar forward seek.
+ */
+ if (s1 >= last)
+ d1 = s1 - last;
+ else if (s1+maxback >= last)
+ d1 = (last - s1)*BACK_PENALTY;
+ else {
+ r1_wrap = 1;
+ d1 = 0; /* shut up, gcc */
+ }
+
+ if (s2 >= last)
+ d2 = s2 - last;
+ else if (s2+maxback >= last)
+ d2 = (last - s2)*BACK_PENALTY;
+ else {
+ r2_wrap = 1;
+ d2 = 0;
+ }
+
+ /* Found required data */
+ if (!r1_wrap && r2_wrap)
+ return arq1;
+ else if (!r2_wrap && r1_wrap)
+ return arq2;
+ else if (r1_wrap && r2_wrap) {
+ /* both behind the head */
+ if (s1 <= s2)
+ return arq1;
+ else
+ return arq2;
+ }
+
+ /* Both requests in front of the head */
+ if (d1 < d2)
+ return arq1;
+ else if (d2 < d1)
+ return arq2;
+ else {
+ if (s1 >= s2)
+ return arq1;
+ else
+ return arq2;
+ }
+}
+
+/*
+ * as_find_next_arq finds the next request after @prev in elevator order.
+ * this with as_choose_req form the basis for how the scheduler chooses
+ * what request to process next. Anticipation works on top of this.
+ */
+static struct as_rq *as_find_next_arq(struct as_data *ad, struct as_rq *last)
+{
+ const int data_dir = last->is_sync;
+ struct as_rq *ret;
+ struct rb_node *rbnext = rb_next(&last->rb_node);
+ struct rb_node *rbprev = rb_prev(&last->rb_node);
+ struct as_rq *arq_next, *arq_prev;
+
+ BUG_ON(!ON_RB(&last->rb_node));
+
+ if (rbprev)
+ arq_prev = rb_entry_arq(rbprev);
+ else
+ arq_prev = NULL;
+
+ if (rbnext)
+ arq_next = rb_entry_arq(rbnext);
+ else {
+ arq_next = as_find_first_arq(ad, data_dir);
+ if (arq_next == last)
+ arq_next = NULL;
+ }
+
+ ret = as_choose_req(ad, arq_next, arq_prev);
+
+ return ret;
+}
+
+/*
+ * anticipatory scheduling functions follow
+ */
+
+/*
+ * as_antic_expired tells us when we have anticipated too long.
+ * The funny "absolute difference" math on the elapsed time is to handle
+ * jiffy wraps, and disks which have been idle for 0x80000000 jiffies.
+ */
+static int as_antic_expired(struct as_data *ad)
+{
+ long delta_jif;
+
+ delta_jif = jiffies - ad->antic_start;
+ if (unlikely(delta_jif < 0))
+ delta_jif = -delta_jif;
+ if (delta_jif < ad->antic_expire)
+ return 0;
+
+ return 1;
+}
+
+/*
+ * as_antic_waitnext starts anticipating that a nice request will soon be
+ * submitted. See also as_antic_waitreq
+ */
+static void as_antic_waitnext(struct as_data *ad)
+{
+ unsigned long timeout;
+
+ BUG_ON(ad->antic_status != ANTIC_OFF
+ && ad->antic_status != ANTIC_WAIT_REQ);
+
+ timeout = ad->antic_start + ad->antic_expire;
+
+ mod_timer(&ad->antic_timer, timeout);
+
+ ad->antic_status = ANTIC_WAIT_NEXT;
+}
+
+/*
+ * as_antic_waitreq starts anticipating. We don't start timing the anticipation
+ * until the request that we're anticipating on has finished. This means we
+ * are timing from when the candidate process wakes up hopefully.
+ */
+static void as_antic_waitreq(struct as_data *ad)
+{
+ BUG_ON(ad->antic_status == ANTIC_FINISHED);
+ if (ad->antic_status == ANTIC_OFF) {
+ if (!ad->io_context || ad->ioc_finished)
+ as_antic_waitnext(ad);
+ else
+ ad->antic_status = ANTIC_WAIT_REQ;
+ }
+}
+
+/*
+ * This is called directly by the functions in this file to stop anticipation.
+ * We kill the timer and schedule a call to the request_fn asap.
+ */
+static void as_antic_stop(struct as_data *ad)
+{
+ int status = ad->antic_status;
+
+ if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) {
+ if (status == ANTIC_WAIT_NEXT)
+ del_timer(&ad->antic_timer);
+ ad->antic_status = ANTIC_FINISHED;
+ /* see as_work_handler */
+ kblockd_schedule_work(&ad->antic_work);
+ }
+}
+
+/*
+ * as_antic_timeout is the timer function set by as_antic_waitnext.
+ */
+static void as_antic_timeout(unsigned long data)
+{
+ struct request_queue *q = (struct request_queue *)data;
+ struct as_data *ad = q->elevator->elevator_data;
+ unsigned long flags;
+
+ spin_lock_irqsave(q->queue_lock, flags);
+ if (ad->antic_status == ANTIC_WAIT_REQ
+ || ad->antic_status == ANTIC_WAIT_NEXT) {
+ struct as_io_context *aic = ad->io_context->aic;
+
+ ad->antic_status = ANTIC_FINISHED;
+ kblockd_schedule_work(&ad->antic_work);
+
+ if (aic->ttime_samples == 0) {
+ /* process anticipated on has exitted or timed out*/
+ ad->exit_prob = (7*ad->exit_prob + 256)/8;
+ }
+ }
+ spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+/*
+ * as_close_req decides if one request is considered "close" to the
+ * previous one issued.
+ */
+static int as_close_req(struct as_data *ad, struct as_rq *arq)
+{
+ unsigned long delay; /* milliseconds */
+ sector_t last = ad->last_sector[ad->batch_data_dir];
+ sector_t next = arq->request->sector;
+ sector_t delta; /* acceptable close offset (in sectors) */
+
+ if (ad->antic_status == ANTIC_OFF || !ad->ioc_finished)
+ delay = 0;
+ else
+ delay = ((jiffies - ad->antic_start) * 1000) / HZ;
+
+ if (delay <= 1)
+ delta = 64;
+ else if (delay <= 20 && delay <= ad->antic_expire)
+ delta = 64 << (delay-1);
+ else
+ return 1;
+
+ return (last - (delta>>1) <= next) && (next <= last + delta);
+}
+
+/*
+ * as_can_break_anticipation returns true if we have been anticipating this
+ * request.
+ *
+ * It also returns true if the process against which we are anticipating
+ * submits a write - that's presumably an fsync, O_SYNC write, etc. We want to
+ * dispatch it ASAP, because we know that application will not be submitting
+ * any new reads.
+ *
+ * If the task which has submitted the request has exitted, break anticipation.
+ *
+ * If this task has queued some other IO, do not enter enticipation.
+ */
+static int as_can_break_anticipation(struct as_data *ad, struct as_rq *arq)
+{
+ struct io_context *ioc;
+ struct as_io_context *aic;
+ sector_t s;
+
+ ioc = ad->io_context;
+ BUG_ON(!ioc);
+
+ if (arq && ioc == arq->io_context) {
+ /* request from same process */
+ return 1;
+ }
+
+ if (ad->ioc_finished && as_antic_expired(ad)) {
+ /*
+ * In this situation status should really be FINISHED,
+ * however the timer hasn't had the chance to run yet.
+ */
+ return 1;
+ }
+
+ aic = ioc->aic;
+ if (!aic)
+ return 0;
+
+ if (!test_bit(AS_TASK_RUNNING, &aic->state)) {
+ /* process anticipated on has exitted */
+ if (aic->ttime_samples == 0)
+ ad->exit_prob = (7*ad->exit_prob + 256)/8;
+ return 1;
+ }
+
+ if (atomic_read(&aic->nr_queued) > 0) {
+ /* process has more requests queued */
+ return 1;
+ }
+
+ if (atomic_read(&aic->nr_dispatched) > 0) {
+ /* process has more requests dispatched */
+ return 1;
+ }
+
+ if (arq && arq->is_sync == REQ_SYNC && as_close_req(ad, arq)) {
+ /*
+ * Found a close request that is not one of ours.
+ *
+ * This makes close requests from another process reset
+ * our thinktime delay. Is generally useful when there are
+ * two or more cooperating processes working in the same
+ * area.
+ */
+ spin_lock(&aic->lock);
+ aic->last_end_request = jiffies;
+ spin_unlock(&aic->lock);
+ return 1;
+ }
+
+
+ if (aic->ttime_samples == 0) {
+ if (ad->new_ttime_mean > ad->antic_expire)
+ return 1;
+ if (ad->exit_prob > 128)
+ return 1;
+ } else if (aic->ttime_mean > ad->antic_expire) {
+ /* the process thinks too much between requests */
+ return 1;
+ }
+
+ if (!arq)
+ return 0;
+
+ if (ad->last_sector[REQ_SYNC] < arq->request->sector)
+ s = arq->request->sector - ad->last_sector[REQ_SYNC];
+ else
+ s = ad->last_sector[REQ_SYNC] - arq->request->sector;
+
+ if (aic->seek_samples == 0) {
+ /*
+ * Process has just started IO. Use past statistics to
+ * guage success possibility
+ */
+ if (ad->new_seek_mean > s) {
+ /* this request is better than what we're expecting */
+ return 1;
+ }
+
+ } else {
+ if (aic->seek_mean > s) {
+ /* this request is better than what we're expecting */
+ return 1;
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * as_can_anticipate indicates weather we should either run arq
+ * or keep anticipating a better request.
+ */
+static int as_can_anticipate(struct as_data *ad, struct as_rq *arq)
+{
+ if (!ad->io_context)
+ /*
+ * Last request submitted was a write
+ */
+ return 0;
+
+ if (ad->antic_status == ANTIC_FINISHED)
+ /*
+ * Don't restart if we have just finished. Run the next request
+ */
+ return 0;
+
+ if (as_can_break_anticipation(ad, arq))
+ /*
+ * This request is a good candidate. Don't keep anticipating,
+ * run it.
+ */
+ return 0;
+
+ /*
+ * OK from here, we haven't finished, and don't have a decent request!
+ * Status is either ANTIC_OFF so start waiting,
+ * ANTIC_WAIT_REQ so continue waiting for request to finish
+ * or ANTIC_WAIT_NEXT so continue waiting for an acceptable request.
+ *
+ */
+
+ return 1;
+}
+
+static void as_update_thinktime(struct as_data *ad, struct as_io_context *aic, unsigned long ttime)
+{
+ /* fixed point: 1.0 == 1<<8 */
+ if (aic->ttime_samples == 0) {
+ ad->new_ttime_total = (7*ad->new_ttime_total + 256*ttime) / 8;
+ ad->new_ttime_mean = ad->new_ttime_total / 256;
+
+ ad->exit_prob = (7*ad->exit_prob)/8;
+ }
+ aic->ttime_samples = (7*aic->ttime_samples + 256) / 8;
+ aic->ttime_total = (7*aic->ttime_total + 256*ttime) / 8;
+ aic->ttime_mean = (aic->ttime_total + 128) / aic->ttime_samples;
+}
+
+static void as_update_seekdist(struct as_data *ad, struct as_io_context *aic, sector_t sdist)
+{
+ u64 total;
+
+ if (aic->seek_samples == 0) {
+ ad->new_seek_total = (7*ad->new_seek_total + 256*(u64)sdist)/8;
+ ad->new_seek_mean = ad->new_seek_total / 256;
+ }
+
+ /*
+ * Don't allow the seek distance to get too large from the
+ * odd fragment, pagein, etc
+ */
+ if (aic->seek_samples <= 60) /* second&third seek */
+ sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*1024);
+ else
+ sdist = min(sdist, (aic->seek_mean * 4) + 2*1024*64);
+
+ aic->seek_samples = (7*aic->seek_samples + 256) / 8;
+ aic->seek_total = (7*aic->seek_total + (u64)256*sdist) / 8;
+ total = aic->seek_total + (aic->seek_samples/2);
+ do_div(total, aic->seek_samples);
+ aic->seek_mean = (sector_t)total;
+}
+
+/*
+ * as_update_iohist keeps a decaying histogram of IO thinktimes, and
+ * updates @aic->ttime_mean based on that. It is called when a new
+ * request is queued.
+ */
+static void as_update_iohist(struct as_data *ad, struct as_io_context *aic, struct request *rq)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+ int data_dir = arq->is_sync;
+ unsigned long thinktime;
+ sector_t seek_dist;
+
+ if (aic == NULL)
+ return;
+
+ if (data_dir == REQ_SYNC) {
+ unsigned long in_flight = atomic_read(&aic->nr_queued)
+ + atomic_read(&aic->nr_dispatched);
+ spin_lock(&aic->lock);
+ if (test_bit(AS_TASK_IORUNNING, &aic->state) ||
+ test_bit(AS_TASK_IOSTARTED, &aic->state)) {
+ /* Calculate read -> read thinktime */
+ if (test_bit(AS_TASK_IORUNNING, &aic->state)
+ && in_flight == 0) {
+ thinktime = jiffies - aic->last_end_request;
+ thinktime = min(thinktime, MAX_THINKTIME-1);
+ } else
+ thinktime = 0;
+ as_update_thinktime(ad, aic, thinktime);
+
+ /* Calculate read -> read seek distance */
+ if (aic->last_request_pos < rq->sector)
+ seek_dist = rq->sector - aic->last_request_pos;
+ else
+ seek_dist = aic->last_request_pos - rq->sector;
+ as_update_seekdist(ad, aic, seek_dist);
+ }
+ aic->last_request_pos = rq->sector + rq->nr_sectors;
+ set_bit(AS_TASK_IOSTARTED, &aic->state);
+ spin_unlock(&aic->lock);
+ }
+}
+
+/*
+ * as_update_arq must be called whenever a request (arq) is added to
+ * the sort_list. This function keeps caches up to date, and checks if the
+ * request might be one we are "anticipating"
+ */
+static void as_update_arq(struct as_data *ad, struct as_rq *arq)
+{
+ const int data_dir = arq->is_sync;
+
+ /* keep the next_arq cache up to date */
+ ad->next_arq[data_dir] = as_choose_req(ad, arq, ad->next_arq[data_dir]);
+
+ /*
+ * have we been anticipating this request?
+ * or does it come from the same process as the one we are anticipating
+ * for?
+ */
+ if (ad->antic_status == ANTIC_WAIT_REQ
+ || ad->antic_status == ANTIC_WAIT_NEXT) {
+ if (as_can_break_anticipation(ad, arq))
+ as_antic_stop(ad);
+ }
+}
+
+/*
+ * Gathers timings and resizes the write batch automatically
+ */
+static void update_write_batch(struct as_data *ad)
+{
+ unsigned long batch = ad->batch_expire[REQ_ASYNC];
+ long write_time;
+
+ write_time = (jiffies - ad->current_batch_expires) + batch;
+ if (write_time < 0)
+ write_time = 0;
+
+ if (write_time > batch && !ad->write_batch_idled) {
+ if (write_time > batch * 3)
+ ad->write_batch_count /= 2;
+ else
+ ad->write_batch_count--;
+ } else if (write_time < batch && ad->current_write_count == 0) {
+ if (batch > write_time * 3)
+ ad->write_batch_count *= 2;
+ else
+ ad->write_batch_count++;
+ }
+
+ if (ad->write_batch_count < 1)
+ ad->write_batch_count = 1;
+}
+
+/*
+ * as_completed_request is to be called when a request has completed and
+ * returned something to the requesting process, be it an error or data.
+ */
+static void as_completed_request(request_queue_t *q, struct request *rq)
+{
+ struct as_data *ad = q->elevator->elevator_data;
+ struct as_rq *arq = RQ_DATA(rq);
+
+ WARN_ON(!list_empty(&rq->queuelist));
+
+ if (arq->state != AS_RQ_REMOVED) {
+ printk("arq->state %d\n", arq->state);
+ WARN_ON(1);
+ goto out;
+ }
+
+ if (ad->changed_batch && ad->nr_dispatched == 1) {
+ kblockd_schedule_work(&ad->antic_work);
+ ad->changed_batch = 0;
+
+ if (ad->batch_data_dir == REQ_SYNC)
+ ad->new_batch = 1;
+ }
+ WARN_ON(ad->nr_dispatched == 0);
+ ad->nr_dispatched--;
+
+ /*
+ * Start counting the batch from when a request of that direction is
+ * actually serviced. This should help devices with big TCQ windows
+ * and writeback caches
+ */
+ if (ad->new_batch && ad->batch_data_dir == arq->is_sync) {
+ update_write_batch(ad);
+ ad->current_batch_expires = jiffies +
+ ad->batch_expire[REQ_SYNC];
+ ad->new_batch = 0;
+ }
+
+ if (ad->io_context == arq->io_context && ad->io_context) {
+ ad->antic_start = jiffies;
+ ad->ioc_finished = 1;
+ if (ad->antic_status == ANTIC_WAIT_REQ) {
+ /*
+ * We were waiting on this request, now anticipate
+ * the next one
+ */
+ as_antic_waitnext(ad);
+ }
+ }
+
+ as_put_io_context(arq);
+out:
+ arq->state = AS_RQ_POSTSCHED;
+}
+
+/*
+ * as_remove_queued_request removes a request from the pre dispatch queue
+ * without updating refcounts. It is expected the caller will drop the
+ * reference unless it replaces the request at somepart of the elevator
+ * (ie. the dispatch queue)
+ */
+static void as_remove_queued_request(request_queue_t *q, struct request *rq)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+ const int data_dir = arq->is_sync;
+ struct as_data *ad = q->elevator->elevator_data;
+
+ WARN_ON(arq->state != AS_RQ_QUEUED);
+
+ if (arq->io_context && arq->io_context->aic) {
+ BUG_ON(!atomic_read(&arq->io_context->aic->nr_queued));
+ atomic_dec(&arq->io_context->aic->nr_queued);
+ }
+
+ /*
+ * Update the "next_arq" cache if we are about to remove its
+ * entry
+ */
+ if (ad->next_arq[data_dir] == arq)
+ ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
+
+ list_del_init(&arq->fifo);
+ as_del_arq_hash(arq);
+ as_del_arq_rb(ad, arq);
+}
+
+/*
+ * as_fifo_expired returns 0 if there are no expired reads on the fifo,
+ * 1 otherwise. It is ratelimited so that we only perform the check once per
+ * `fifo_expire' interval. Otherwise a large number of expired requests
+ * would create a hopeless seekstorm.
+ *
+ * See as_antic_expired comment.
+ */
+static int as_fifo_expired(struct as_data *ad, int adir)
+{
+ struct as_rq *arq;
+ long delta_jif;
+
+ delta_jif = jiffies - ad->last_check_fifo[adir];
+ if (unlikely(delta_jif < 0))
+ delta_jif = -delta_jif;
+ if (delta_jif < ad->fifo_expire[adir])
+ return 0;
+
+ ad->last_check_fifo[adir] = jiffies;
+
+ if (list_empty(&ad->fifo_list[adir]))
+ return 0;
+
+ arq = list_entry_fifo(ad->fifo_list[adir].next);
+
+ return time_after(jiffies, arq->expires);
+}
+
+/*
+ * as_batch_expired returns true if the current batch has expired. A batch
+ * is a set of reads or a set of writes.
+ */
+static inline int as_batch_expired(struct as_data *ad)
+{
+ if (ad->changed_batch || ad->new_batch)
+ return 0;
+
+ if (ad->batch_data_dir == REQ_SYNC)
+ /* TODO! add a check so a complete fifo gets written? */
+ return time_after(jiffies, ad->current_batch_expires);
+
+ return time_after(jiffies, ad->current_batch_expires)
+ || ad->current_write_count == 0;
+}
+
+/*
+ * move an entry to dispatch queue
+ */
+static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
+{
+ struct request *rq = arq->request;
+ const int data_dir = arq->is_sync;
+
+ BUG_ON(!ON_RB(&arq->rb_node));
+
+ as_antic_stop(ad);
+ ad->antic_status = ANTIC_OFF;
+
+ /*
+ * This has to be set in order to be correctly updated by
+ * as_find_next_arq
+ */
+ ad->last_sector[data_dir] = rq->sector + rq->nr_sectors;
+
+ if (data_dir == REQ_SYNC) {
+ /* In case we have to anticipate after this */
+ copy_io_context(&ad->io_context, &arq->io_context);
+ } else {
+ if (ad->io_context) {
+ put_io_context(ad->io_context);
+ ad->io_context = NULL;
+ }
+
+ if (ad->current_write_count != 0)
+ ad->current_write_count--;
+ }
+ ad->ioc_finished = 0;
+
+ ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
+
+ /*
+ * take it off the sort and fifo list, add to dispatch queue
+ */
+ while (!list_empty(&rq->queuelist)) {
+ struct request *__rq = list_entry_rq(rq->queuelist.next);
+ struct as_rq *__arq = RQ_DATA(__rq);
+
+ list_del(&__rq->queuelist);
+
+ elv_dispatch_add_tail(ad->q, __rq);
+
+ if (__arq->io_context && __arq->io_context->aic)
+ atomic_inc(&__arq->io_context->aic->nr_dispatched);
+
+ WARN_ON(__arq->state != AS_RQ_QUEUED);
+ __arq->state = AS_RQ_DISPATCHED;
+
+ ad->nr_dispatched++;
+ }
+
+ as_remove_queued_request(ad->q, rq);
+ WARN_ON(arq->state != AS_RQ_QUEUED);
+
+ elv_dispatch_sort(ad->q, rq);
+
+ arq->state = AS_RQ_DISPATCHED;
+ if (arq->io_context && arq->io_context->aic)
+ atomic_inc(&arq->io_context->aic->nr_dispatched);
+ ad->nr_dispatched++;
+}
+
+/*
+ * as_dispatch_request selects the best request according to
+ * read/write expire, batch expire, etc, and moves it to the dispatch
+ * queue. Returns 1 if a request was found, 0 otherwise.
+ */
+static int as_dispatch_request(request_queue_t *q, int force)
+{
+ struct as_data *ad = q->elevator->elevator_data;
+ struct as_rq *arq;
+ const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]);
+ const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]);
+
+ if (unlikely(force)) {
+ /*
+ * Forced dispatch, accounting is useless. Reset
+ * accounting states and dump fifo_lists. Note that
+ * batch_data_dir is reset to REQ_SYNC to avoid
+ * screwing write batch accounting as write batch
+ * accounting occurs on W->R transition.
+ */
+ int dispatched = 0;
+
+ ad->batch_data_dir = REQ_SYNC;
+ ad->changed_batch = 0;
+ ad->new_batch = 0;
+
+ while (ad->next_arq[REQ_SYNC]) {
+ as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
+ dispatched++;
+ }
+ ad->last_check_fifo[REQ_SYNC] = jiffies;
+
+ while (ad->next_arq[REQ_ASYNC]) {
+ as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]);
+ dispatched++;
+ }
+ ad->last_check_fifo[REQ_ASYNC] = jiffies;
+
+ return dispatched;
+ }
+
+ /* Signal that the write batch was uncontended, so we can't time it */
+ if (ad->batch_data_dir == REQ_ASYNC && !reads) {
+ if (ad->current_write_count == 0 || !writes)
+ ad->write_batch_idled = 1;
+ }
+
+ if (!(reads || writes)
+ || ad->antic_status == ANTIC_WAIT_REQ
+ || ad->antic_status == ANTIC_WAIT_NEXT
+ || ad->changed_batch)
+ return 0;
+
+ if (!(reads && writes && as_batch_expired(ad)) ) {
+ /*
+ * batch is still running or no reads or no writes
+ */
+ arq = ad->next_arq[ad->batch_data_dir];
+
+ if (ad->batch_data_dir == REQ_SYNC && ad->antic_expire) {
+ if (as_fifo_expired(ad, REQ_SYNC))
+ goto fifo_expired;
+
+ if (as_can_anticipate(ad, arq)) {
+ as_antic_waitreq(ad);
+ return 0;
+ }
+ }
+
+ if (arq) {
+ /* we have a "next request" */
+ if (reads && !writes)
+ ad->current_batch_expires =
+ jiffies + ad->batch_expire[REQ_SYNC];
+ goto dispatch_request;
+ }
+ }
+
+ /*
+ * at this point we are not running a batch. select the appropriate
+ * data direction (read / write)
+ */
+
+ if (reads) {
+ BUG_ON(RB_EMPTY(&ad->sort_list[REQ_SYNC]));
+
+ if (writes && ad->batch_data_dir == REQ_SYNC)
+ /*
+ * Last batch was a read, switch to writes
+ */
+ goto dispatch_writes;
+
+ if (ad->batch_data_dir == REQ_ASYNC) {
+ WARN_ON(ad->new_batch);
+ ad->changed_batch = 1;
+ }
+ ad->batch_data_dir = REQ_SYNC;
+ arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
+ ad->last_check_fifo[ad->batch_data_dir] = jiffies;
+ goto dispatch_request;
+ }
+
+ /*
+ * the last batch was a read
+ */
+
+ if (writes) {
+dispatch_writes:
+ BUG_ON(RB_EMPTY(&ad->sort_list[REQ_ASYNC]));
+
+ if (ad->batch_data_dir == REQ_SYNC) {
+ ad->changed_batch = 1;
+
+ /*
+ * new_batch might be 1 when the queue runs out of
+ * reads. A subsequent submission of a write might
+ * cause a change of batch before the read is finished.
+ */
+ ad->new_batch = 0;
+ }
+ ad->batch_data_dir = REQ_ASYNC;
+ ad->current_write_count = ad->write_batch_count;
+ ad->write_batch_idled = 0;
+ arq = ad->next_arq[ad->batch_data_dir];
+ goto dispatch_request;
+ }
+
+ BUG();
+ return 0;
+
+dispatch_request:
+ /*
+ * If a request has expired, service it.
+ */
+
+ if (as_fifo_expired(ad, ad->batch_data_dir)) {
+fifo_expired:
+ arq = list_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
+ BUG_ON(arq == NULL);
+ }
+
+ if (ad->changed_batch) {
+ WARN_ON(ad->new_batch);
+
+ if (ad->nr_dispatched)
+ return 0;
+
+ if (ad->batch_data_dir == REQ_ASYNC)
+ ad->current_batch_expires = jiffies +
+ ad->batch_expire[REQ_ASYNC];
+ else
+ ad->new_batch = 1;
+
+ ad->changed_batch = 0;
+ }
+
+ /*
+ * arq is the selected appropriate request.
+ */
+ as_move_to_dispatch(ad, arq);
+
+ return 1;
+}
+
+/*
+ * Add arq to a list behind alias
+ */
+static inline void
+as_add_aliased_request(struct as_data *ad, struct as_rq *arq, struct as_rq *alias)
+{
+ struct request *req = arq->request;
+ struct list_head *insert = alias->request->queuelist.prev;
+
+ /*
+ * Transfer list of aliases
+ */
+ while (!list_empty(&req->queuelist)) {
+ struct request *__rq = list_entry_rq(req->queuelist.next);
+ struct as_rq *__arq = RQ_DATA(__rq);
+
+ list_move_tail(&__rq->queuelist, &alias->request->queuelist);
+
+ WARN_ON(__arq->state != AS_RQ_QUEUED);
+ }
+
+ /*
+ * Another request with the same start sector on the rbtree.
+ * Link this request to that sector. They are untangled in
+ * as_move_to_dispatch
+ */
+ list_add(&arq->request->queuelist, insert);
+
+ /*
+ * Don't want to have to handle merges.
+ */
+ as_del_arq_hash(arq);
+ arq->request->flags |= REQ_NOMERGE;
+}
+
+/*
+ * add arq to rbtree and fifo
+ */
+static void as_add_request(request_queue_t *q, struct request *rq)
+{
+ struct as_data *ad = q->elevator->elevator_data;
+ struct as_rq *arq = RQ_DATA(rq);
+ struct as_rq *alias;
+ int data_dir;
+
+ if (arq->state != AS_RQ_PRESCHED) {
+ printk("arq->state: %d\n", arq->state);
+ WARN_ON(1);
+ }
+ arq->state = AS_RQ_NEW;
+
+ if (rq_data_dir(arq->request) == READ
+ || current->flags&PF_SYNCWRITE)
+ arq->is_sync = 1;
+ else
+ arq->is_sync = 0;
+ data_dir = arq->is_sync;
+
+ arq->io_context = as_get_io_context();
+
+ if (arq->io_context) {
+ as_update_iohist(ad, arq->io_context->aic, arq->request);
+ atomic_inc(&arq->io_context->aic->nr_queued);
+ }
+
+ alias = as_add_arq_rb(ad, arq);
+ if (!alias) {
+ /*
+ * set expire time (only used for reads) and add to fifo list
+ */
+ arq->expires = jiffies + ad->fifo_expire[data_dir];
+ list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]);
+
+ if (rq_mergeable(arq->request))
+ as_add_arq_hash(ad, arq);
+ as_update_arq(ad, arq); /* keep state machine up to date */
+
+ } else {
+ as_add_aliased_request(ad, arq, alias);
+
+ /*
+ * have we been anticipating this request?
+ * or does it come from the same process as the one we are
+ * anticipating for?
+ */
+ if (ad->antic_status == ANTIC_WAIT_REQ
+ || ad->antic_status == ANTIC_WAIT_NEXT) {
+ if (as_can_break_anticipation(ad, arq))
+ as_antic_stop(ad);
+ }
+ }
+
+ arq->state = AS_RQ_QUEUED;
+}
+
+static void as_activate_request(request_queue_t *q, struct request *rq)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+
+ WARN_ON(arq->state != AS_RQ_DISPATCHED);
+ arq->state = AS_RQ_REMOVED;
+ if (arq->io_context && arq->io_context->aic)
+ atomic_dec(&arq->io_context->aic->nr_dispatched);
+}
+
+static void as_deactivate_request(request_queue_t *q, struct request *rq)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+
+ WARN_ON(arq->state != AS_RQ_REMOVED);
+ arq->state = AS_RQ_DISPATCHED;
+ if (arq->io_context && arq->io_context->aic)
+ atomic_inc(&arq->io_context->aic->nr_dispatched);
+}
+
+/*
+ * as_queue_empty tells us if there are requests left in the device. It may
+ * not be the case that a driver can get the next request even if the queue
+ * is not empty - it is used in the block layer to check for plugging and
+ * merging opportunities
+ */
+static int as_queue_empty(request_queue_t *q)
+{
+ struct as_data *ad = q->elevator->elevator_data;
+
+ return list_empty(&ad->fifo_list[REQ_ASYNC])
+ && list_empty(&ad->fifo_list[REQ_SYNC]);
+}
+
+static struct request *
+as_former_request(request_queue_t *q, struct request *rq)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+ struct rb_node *rbprev = rb_prev(&arq->rb_node);
+ struct request *ret = NULL;
+
+ if (rbprev)
+ ret = rb_entry_arq(rbprev)->request;
+
+ return ret;
+}
+
+static struct request *
+as_latter_request(request_queue_t *q, struct request *rq)
+{
+ struct as_rq *arq = RQ_DATA(rq);
+ struct rb_node *rbnext = rb_next(&arq->rb_node);
+ struct request *ret = NULL;
+
+ if (rbnext)
+ ret = rb_entry_arq(rbnext)->request;
+
+ return ret;
+}
+
+static int
+as_merge(request_queue_t *q, struct request **req, struct bio *bio)
+{
+ struct as_data *ad = q->elevator->elevator_data;
+ sector_t rb_key = bio->bi_sector + bio_sectors(bio);
+ struct request *__rq;
+ int ret;
+
+ /*
+ * see if the merge hash can satisfy a back merge
+ */
+ __rq = as_find_arq_hash(ad, bio->bi_sector);
+ if (__rq) {
+ BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
+
+ if (elv_rq_merge_ok(__rq, bio)) {
+ ret = ELEVATOR_BACK_MERGE;
+ goto out;
+ }
+ }
+
+ /*
+ * check for front merge
+ */
+ __rq = as_find_arq_rb(ad, rb_key, bio_data_dir(bio));
+ if (__rq) {
+ BUG_ON(rb_key != rq_rb_key(__rq));
+
+ if (elv_rq_merge_ok(__rq, bio)) {
+ ret = ELEVATOR_FRONT_MERGE;
+ goto out;
+ }
+ }
+
+ return ELEVATOR_NO_MERGE;
+out:
+ if (ret) {
+ if (rq_mergeable(__rq))
+ as_hot_arq_hash(ad, RQ_DATA(__rq));
+ }
+ *req = __rq;
+ return ret;
+}
+
+static void as_merged_request(request_queue_t *q, struct request *req)
+{
+ struct as_data *ad = q->elevator->elevator_data;
+ struct as_rq *arq = RQ_DATA(req);
+
+ /*
+ * hash always needs to be repositioned, key is end sector
+ */
+ as_del_arq_hash(arq);
+ as_add_arq_hash(ad, arq);
+
+ /*
+ * if the merge was a front merge, we need to reposition request
+ */
+ if (rq_rb_key(req) != arq->rb_key) {
+ struct as_rq *alias, *next_arq = NULL;
+
+ if (ad->next_arq[arq->is_sync] == arq)
+ next_arq = as_find_next_arq(ad, arq);
+
+ /*
+ * Note! We should really be moving any old aliased requests
+ * off this request and try to insert them into the rbtree. We
+ * currently don't bother. Ditto the next function.
+ */
+ as_del_arq_rb(ad, arq);
+ if ((alias = as_add_arq_rb(ad, arq)) ) {
+ list_del_init(&arq->fifo);
+ as_add_aliased_request(ad, arq, alias);
+ if (next_arq)
+ ad->next_arq[arq->is_sync] = next_arq;
+ }
+ /*
+ * Note! At this stage of this and the next function, our next
+ * request may not be optimal - eg the request may have "grown"
+ * behind the disk head. We currently don't bother adjusting.
+ */
+ }
+}
+
+static void
+as_merged_requests(request_queue_t *q, struct request *req,
+ struct request *next)
+{
+ struct as_data *ad = q->elevator->elevator_data;
+ struct as_rq *arq = RQ_DATA(req);
+ struct as_rq *anext = RQ_DATA(next);
+
+ BUG_ON(!arq);
+ BUG_ON(!anext);
+
+ /*
+ * reposition arq (this is the merged request) in hash, and in rbtree
+ * in case of a front merge
+ */
+ as_del_arq_hash(arq);
+ as_add_arq_hash(ad, arq);
+
+ if (rq_rb_key(req) != arq->rb_key) {
+ struct as_rq *alias, *next_arq = NULL;
+
+ if (ad->next_arq[arq->is_sync] == arq)
+ next_arq = as_find_next_arq(ad, arq);
+
+ as_del_arq_rb(ad, arq);
+ if ((alias = as_add_arq_rb(ad, arq)) ) {
+ list_del_init(&arq->fifo);
+ as_add_aliased_request(ad, arq, alias);
+ if (next_arq)
+ ad->next_arq[arq->is_sync] = next_arq;
+ }
+ }
+
+ /*
+ * if anext expires before arq, assign its expire time to arq
+ * and move into anext position (anext will be deleted) in fifo
+ */
+ if (!list_empty(&arq->fifo) && !list_empty(&anext->fifo)) {
+ if (time_before(anext->expires, arq->expires)) {
+ list_move(&arq->fifo, &anext->fifo);
+ arq->expires = anext->expires;
+ /*
+ * Don't copy here but swap, because when anext is
+ * removed below, it must contain the unused context
+ */
+ swap_io_context(&arq->io_context, &anext->io_context);
+ }
+ }
+
+ /*
+ * Transfer list of aliases
+ */
+ while (!list_empty(&next->queuelist)) {
+ struct request *__rq = list_entry_rq(next->queuelist.next);
+ struct as_rq *__arq = RQ_DATA(__rq);
+
+ list_move_tail(&__rq->queuelist, &req->queuelist);
+
+ WARN_ON(__arq->state != AS_RQ_QUEUED);
+ }
+
+ /*
+ * kill knowledge of next, this one is a goner
+ */
+ as_remove_queued_request(q, next);
+ as_put_io_context(anext);
+
+ anext->state = AS_RQ_MERGED;
+}
+
+/*
+ * This is executed in a "deferred" process context, by kblockd. It calls the
+ * driver's request_fn so the driver can submit that request.
+ *
+ * IMPORTANT! This guy will reenter the elevator, so set up all queue global
+ * state before calling, and don't rely on any state over calls.
+ *
+ * FIXME! dispatch queue is not a queue at all!
+ */
+static void as_work_handler(void *data)
+{
+ struct request_queue *q = data;
+ unsigned long flags;
+
+ spin_lock_irqsave(q->queue_lock, flags);
+ if (!as_queue_empty(q))
+ q->request_fn(q);
+ spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+static void as_put_request(request_queue_t *q, struct request *rq)
+{
+ struct as_data *ad = q->elevator->elevator_data;
+ struct as_rq *arq = RQ_DATA(rq);
+
+ if (!arq) {
+ WARN_ON(1);
+ return;
+ }
+
+ if (unlikely(arq->state != AS_RQ_POSTSCHED &&
+ arq->state != AS_RQ_PRESCHED &&
+ arq->state != AS_RQ_MERGED)) {
+ printk("arq->state %d\n", arq->state);
+ WARN_ON(1);
+ }
+
+ mempool_free(arq, ad->arq_pool);
+ rq->elevator_private = NULL;
+}
+
+static int as_set_request(request_queue_t *q, struct request *rq,
+ struct bio *bio, gfp_t gfp_mask)
+{
+ struct as_data *ad = q->elevator->elevator_data;
+ struct as_rq *arq = mempool_alloc(ad->arq_pool, gfp_mask);
+
+ if (arq) {
+ memset(arq, 0, sizeof(*arq));
+ RB_CLEAR(&arq->rb_node);
+ arq->request = rq;
+ arq->state = AS_RQ_PRESCHED;
+ arq->io_context = NULL;
+ INIT_LIST_HEAD(&arq->hash);
+ arq->on_hash = 0;
+ INIT_LIST_HEAD(&arq->fifo);
+ rq->elevator_private = arq;
+ return 0;
+ }
+
+ return 1;
+}
+
+static int as_may_queue(request_queue_t *q, int rw, struct bio *bio)
+{
+ int ret = ELV_MQUEUE_MAY;
+ struct as_data *ad = q->elevator->elevator_data;
+ struct io_context *ioc;
+ if (ad->antic_status == ANTIC_WAIT_REQ ||
+ ad->antic_status == ANTIC_WAIT_NEXT) {
+ ioc = as_get_io_context();
+ if (ad->io_context == ioc)
+ ret = ELV_MQUEUE_MUST;
+ put_io_context(ioc);
+ }
+
+ return ret;
+}
+
+static void as_exit_queue(elevator_t *e)
+{
+ struct as_data *ad = e->elevator_data;
+
+ del_timer_sync(&ad->antic_timer);
+ kblockd_flush();
+
+ BUG_ON(!list_empty(&ad->fifo_list[REQ_SYNC]));
+ BUG_ON(!list_empty(&ad->fifo_list[REQ_ASYNC]));
+
+ mempool_destroy(ad->arq_pool);
+ put_io_context(ad->io_context);
+ kfree(ad->hash);
+ kfree(ad);
+}
+
+/*
+ * initialize elevator private data (as_data), and alloc a arq for
+ * each request on the free lists
+ */
+static int as_init_queue(request_queue_t *q, elevator_t *e)
+{
+ struct as_data *ad;
+ int i;
+
+ if (!arq_pool)
+ return -ENOMEM;
+
+ ad = kmalloc_node(sizeof(*ad), GFP_KERNEL, q->node);
+ if (!ad)
+ return -ENOMEM;
+ memset(ad, 0, sizeof(*ad));
+
+ ad->q = q; /* Identify what queue the data belongs to */
+
+ ad->hash = kmalloc_node(sizeof(struct list_head)*AS_HASH_ENTRIES,
+ GFP_KERNEL, q->node);
+ if (!ad->hash) {
+ kfree(ad);
+ return -ENOMEM;
+ }
+
+ ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
+ mempool_free_slab, arq_pool, q->node);
+ if (!ad->arq_pool) {
+ kfree(ad->hash);
+ kfree(ad);
+ return -ENOMEM;
+ }
+
+ /* anticipatory scheduling helpers */
+ ad->antic_timer.function = as_antic_timeout;
+ ad->antic_timer.data = (unsigned long)q;
+ init_timer(&ad->antic_timer);
+ INIT_WORK(&ad->antic_work, as_work_handler, q);
+
+ for (i = 0; i < AS_HASH_ENTRIES; i++)
+ INIT_LIST_HEAD(&ad->hash[i]);
+
+ INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]);
+ INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]);
+ ad->sort_list[REQ_SYNC] = RB_ROOT;
+ ad->sort_list[REQ_ASYNC] = RB_ROOT;
+ ad->fifo_expire[REQ_SYNC] = default_read_expire;
+ ad->fifo_expire[REQ_ASYNC] = default_write_expire;
+ ad->antic_expire = default_antic_expire;
+ ad->batch_expire[REQ_SYNC] = default_read_batch_expire;
+ ad->batch_expire[REQ_ASYNC] = default_write_batch_expire;
+ e->elevator_data = ad;
+
+ ad->current_batch_expires = jiffies + ad->batch_expire[REQ_SYNC];
+ ad->write_batch_count = ad->batch_expire[REQ_ASYNC] / 10;
+ if (ad->write_batch_count < 2)
+ ad->write_batch_count = 2;
+
+ return 0;
+}
+
+/*
+ * sysfs parts below
+ */
+struct as_fs_entry {
+ struct attribute attr;
+ ssize_t (*show)(struct as_data *, char *);
+ ssize_t (*store)(struct as_data *, const char *, size_t);
+};
+
+static ssize_t
+as_var_show(unsigned int var, char *page)
+{
+ return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+as_var_store(unsigned long *var, const char *page, size_t count)
+{
+ char *p = (char *) page;
+
+ *var = simple_strtoul(p, &p, 10);
+ return count;
+}
+
+static ssize_t as_est_show(struct as_data *ad, char *page)
+{
+ int pos = 0;
+
+ pos += sprintf(page+pos, "%lu %% exit probability\n", 100*ad->exit_prob/256);
+ pos += sprintf(page+pos, "%lu ms new thinktime\n", ad->new_ttime_mean);
+ pos += sprintf(page+pos, "%llu sectors new seek distance\n", (unsigned long long)ad->new_seek_mean);
+
+ return pos;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR) \
+static ssize_t __FUNC(struct as_data *ad, char *page) \
+{ \
+ return as_var_show(jiffies_to_msecs((__VAR)), (page)); \
+}
+SHOW_FUNCTION(as_readexpire_show, ad->fifo_expire[REQ_SYNC]);
+SHOW_FUNCTION(as_writeexpire_show, ad->fifo_expire[REQ_ASYNC]);
+SHOW_FUNCTION(as_anticexpire_show, ad->antic_expire);
+SHOW_FUNCTION(as_read_batchexpire_show, ad->batch_expire[REQ_SYNC]);
+SHOW_FUNCTION(as_write_batchexpire_show, ad->batch_expire[REQ_ASYNC]);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
+static ssize_t __FUNC(struct as_data *ad, const char *page, size_t count) \
+{ \
+ int ret = as_var_store(__PTR, (page), count); \
+ if (*(__PTR) < (MIN)) \
+ *(__PTR) = (MIN); \
+ else if (*(__PTR) > (MAX)) \
+ *(__PTR) = (MAX); \
+ *(__PTR) = msecs_to_jiffies(*(__PTR)); \
+ return ret; \
+}
+STORE_FUNCTION(as_readexpire_store, &ad->fifo_expire[REQ_SYNC], 0, INT_MAX);
+STORE_FUNCTION(as_writeexpire_store, &ad->fifo_expire[REQ_ASYNC], 0, INT_MAX);
+STORE_FUNCTION(as_anticexpire_store, &ad->antic_expire, 0, INT_MAX);
+STORE_FUNCTION(as_read_batchexpire_store,
+ &ad->batch_expire[REQ_SYNC], 0, INT_MAX);
+STORE_FUNCTION(as_write_batchexpire_store,
+ &ad->batch_expire[REQ_ASYNC], 0, INT_MAX);
+#undef STORE_FUNCTION
+
+static struct as_fs_entry as_est_entry = {
+ .attr = {.name = "est_time", .mode = S_IRUGO },
+ .show = as_est_show,
+};
+static struct as_fs_entry as_readexpire_entry = {
+ .attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = as_readexpire_show,
+ .store = as_readexpire_store,
+};
+static struct as_fs_entry as_writeexpire_entry = {
+ .attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = as_writeexpire_show,
+ .store = as_writeexpire_store,
+};
+static struct as_fs_entry as_anticexpire_entry = {
+ .attr = {.name = "antic_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = as_anticexpire_show,
+ .store = as_anticexpire_store,
+};
+static struct as_fs_entry as_read_batchexpire_entry = {
+ .attr = {.name = "read_batch_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = as_read_batchexpire_show,
+ .store = as_read_batchexpire_store,
+};
+static struct as_fs_entry as_write_batchexpire_entry = {
+ .attr = {.name = "write_batch_expire", .mode = S_IRUGO | S_IWUSR },
+ .show = as_write_batchexpire_show,
+ .store = as_write_batchexpire_store,
+};
+
+static struct attribute *default_attrs[] = {
+ &as_est_entry.attr,
+ &as_readexpire_entry.attr,
+ &as_writeexpire_entry.attr,
+ &as_anticexpire_entry.attr,
+ &as_read_batchexpire_entry.attr,
+ &as_write_batchexpire_entry.attr,
+ NULL,
+};
+
+#define to_as(atr) container_of((atr), struct as_fs_entry, attr)
+
+static ssize_t
+as_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
+{
+ elevator_t *e = container_of(kobj, elevator_t, kobj);
+ struct as_fs_entry *entry = to_as(attr);
+
+ if (!entry->show)
+ return -EIO;
+
+ return entry->show(e->elevator_data, page);
+}
+
+static ssize_t
+as_attr_store(struct kobject *kobj, struct attribute *attr,
+ const char *page, size_t length)
+{
+ elevator_t *e = container_of(kobj, elevator_t, kobj);
+ struct as_fs_entry *entry = to_as(attr);
+
+ if (!entry->store)
+ return -EIO;
+
+ return entry->store(e->elevator_data, page, length);
+}
+
+static struct sysfs_ops as_sysfs_ops = {
+ .show = as_attr_show,
+ .store = as_attr_store,
+};
+
+static struct kobj_type as_ktype = {
+ .sysfs_ops = &as_sysfs_ops,
+ .default_attrs = default_attrs,
+};
+
+static struct elevator_type iosched_as = {
+ .ops = {
+ .elevator_merge_fn = as_merge,
+ .elevator_merged_fn = as_merged_request,
+ .elevator_merge_req_fn = as_merged_requests,
+ .elevator_dispatch_fn = as_dispatch_request,
+ .elevator_add_req_fn = as_add_request,
+ .elevator_activate_req_fn = as_activate_request,
+ .elevator_deactivate_req_fn = as_deactivate_request,
+ .elevator_queue_empty_fn = as_queue_empty,
+ .elevator_completed_req_fn = as_completed_request,
+ .elevator_former_req_fn = as_former_request,
+ .elevator_latter_req_fn = as_latter_request,
+ .elevator_set_req_fn = as_set_request,
+ .elevator_put_req_fn = as_put_request,
+ .elevator_may_queue_fn = as_may_queue,
+ .elevator_init_fn = as_init_queue,
+ .elevator_exit_fn = as_exit_queue,
+ },
+
+ .elevator_ktype = &as_ktype,
+ .elevator_name = "anticipatory",
+ .elevator_owner = THIS_MODULE,
+};
+
+static int __init as_init(void)
+{
+ int ret;
+
+ arq_pool = kmem_cache_create("as_arq", sizeof(struct as_rq),
+ 0, 0, NULL, NULL);
+ if (!arq_pool)
+ return -ENOMEM;
+
+ ret = elv_register(&iosched_as);
+ if (!ret) {
+ /*
+ * don't allow AS to get unregistered, since we would have
+ * to browse all tasks in the system and release their
+ * as_io_context first
+ */
+ __module_get(THIS_MODULE);
+ return 0;
+ }
+
+ kmem_cache_destroy(arq_pool);
+ return ret;
+}
+
+static void __exit as_exit(void)
+{
+ elv_unregister(&iosched_as);
+ kmem_cache_destroy(arq_pool);
+}
+
+module_init(as_init);
+module_exit(as_exit);
+
+MODULE_AUTHOR("Nick Piggin");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("anticipatory IO scheduler");