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cfq-iosched: get rid of the need for __GFP_NOFAIL in cfq_find_alloc_queue()

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Setup an emergency fallback cfqq that we allocate at IO scheduler init
time. If the slab allocation fails in cfq_find_alloc_queue(), we'll just
punt IO to that cfqq instead. This ensures that cfq_find_alloc_queue()
never fails without having to ensure free memory.

On cfqq lookup, always try to allocate a new cfqq if the given cfq io
context has the oom_cfqq assigned. This ensures that we only temporarily
punt to this shared queue.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2009-06-30 09:34:12 +02:00
parent d5036d770f
commit 6118b70b3a
1 changed files with 73 additions and 64 deletions
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137
block/cfq-iosched.c
View file

@ -70,6 +70,51 @@ struct cfq_rb_root {
};
#define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, }
/*
* Per process-grouping structure
*/
struct cfq_queue {
/* reference count */
atomic_t ref;
/* various state flags, see below */
unsigned int flags;
/* parent cfq_data */
struct cfq_data *cfqd;
/* service_tree member */
struct rb_node rb_node;
/* service_tree key */
unsigned long rb_key;
/* prio tree member */
struct rb_node p_node;
/* prio tree root we belong to, if any */
struct rb_root *p_root;
/* sorted list of pending requests */
struct rb_root sort_list;
/* if fifo isn't expired, next request to serve */
struct request *next_rq;
/* requests queued in sort_list */
int queued[2];
/* currently allocated requests */
int allocated[2];
/* fifo list of requests in sort_list */
struct list_head fifo;
unsigned long slice_end;
long slice_resid;
unsigned int slice_dispatch;
/* pending metadata requests */
int meta_pending;
/* number of requests that are on the dispatch list or inside driver */
int dispatched;
/* io prio of this group */
unsigned short ioprio, org_ioprio;
unsigned short ioprio_class, org_ioprio_class;
pid_t pid;
};
/*
* Per block device queue structure
*/
@ -135,51 +180,11 @@ struct cfq_data {
unsigned int cfq_slice_idle;
struct list_head cic_list;
};
/*
* Per process-grouping structure
*/
struct cfq_queue {
/* reference count */
atomic_t ref;
/* various state flags, see below */
unsigned int flags;
/* parent cfq_data */
struct cfq_data *cfqd;
/* service_tree member */
struct rb_node rb_node;
/* service_tree key */
unsigned long rb_key;
/* prio tree member */
struct rb_node p_node;
/* prio tree root we belong to, if any */
struct rb_root *p_root;
/* sorted list of pending requests */
struct rb_root sort_list;
/* if fifo isn't expired, next request to serve */
struct request *next_rq;
/* requests queued in sort_list */
int queued[2];
/* currently allocated requests */
int allocated[2];
/* fifo list of requests in sort_list */
struct list_head fifo;
unsigned long slice_end;
long slice_resid;
unsigned int slice_dispatch;
/* pending metadata requests */
int meta_pending;
/* number of requests that are on the dispatch list or inside driver */
int dispatched;
/* io prio of this group */
unsigned short ioprio, org_ioprio;
unsigned short ioprio_class, org_ioprio_class;
pid_t pid;
/*
* Fallback dummy cfqq for extreme OOM conditions
*/
struct cfq_queue oom_cfqq;
};
enum cfqq_state_flags {
@ -1673,41 +1678,40 @@ retry:
/* cic always exists here */
cfqq = cic_to_cfqq(cic, is_sync);
if (!cfqq) {
/*
* Always try a new alloc if we fell back to the OOM cfqq
* originally, since it should just be a temporary situation.
*/
if (!cfqq || cfqq == &cfqd->oom_cfqq) {
cfqq = NULL;
if (new_cfqq) {
cfqq = new_cfqq;
new_cfqq = NULL;
} else if (gfp_mask & __GFP_WAIT) {
/*
* Inform the allocator of the fact that we will
* just repeat this allocation if it fails, to allow
* the allocator to do whatever it needs to attempt to
* free memory.
*/
spin_unlock_irq(cfqd->queue->queue_lock);
new_cfqq = kmem_cache_alloc_node(cfq_pool,
gfp_mask | __GFP_NOFAIL | __GFP_ZERO,
gfp_mask | __GFP_ZERO,
cfqd->queue->node);
spin_lock_irq(cfqd->queue->queue_lock);
goto retry;
if (new_cfqq)
goto retry;
} else {
cfqq = kmem_cache_alloc_node(cfq_pool,
gfp_mask | __GFP_ZERO,
cfqd->queue->node);
if (!cfqq)
goto out;
}
cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
cfq_init_prio_data(cfqq, ioc);
cfq_log_cfqq(cfqd, cfqq, "alloced");
if (cfqq) {
cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
cfq_init_prio_data(cfqq, ioc);
cfq_log_cfqq(cfqd, cfqq, "alloced");
} else
cfqq = &cfqd->oom_cfqq;
}
if (new_cfqq)
kmem_cache_free(cfq_pool, new_cfqq);
out:
WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
return cfqq;
}
@ -1740,11 +1744,8 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
cfqq = *async_cfqq;
}
if (!cfqq) {
if (!cfqq)
cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
if (!cfqq)
return NULL;
}
/*
* pin the queue now that it's allocated, scheduler exit will prune it
@ -2470,6 +2471,14 @@ static void *cfq_init_queue(struct request_queue *q)
for (i = 0; i < CFQ_PRIO_LISTS; i++)
cfqd->prio_trees[i] = RB_ROOT;
/*
* Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
* Grab a permanent reference to it, so that the normal code flow
* will not attempt to free it.
*/
cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
atomic_inc(&cfqd->oom_cfqq.ref);
INIT_LIST_HEAD(&cfqd->cic_list);
cfqd->queue = q;