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#include "ceph_debug.h"
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/vmalloc.h>
#include "msgpool.h"
/*
* We use msg pools to preallocate memory for messages we expect to
* receive over the wire, to avoid getting ourselves into OOM
* conditions at unexpected times. We take use a few different
* strategies:
*
* - for request/response type interactions, we preallocate the
* memory needed for the response when we generate the request.
*
* - for messages we can receive at any time from the MDS, we preallocate
* a pool of messages we can re-use.
*
* - for writeback, we preallocate some number of messages to use for
* requests and their replies, so that we always make forward
* progress.
*
* The msgpool behaves like a mempool_t, but keeps preallocated
* ceph_msgs strung together on a list_head instead of using a pointer
* vector. This avoids vector reallocation when we adjust the number
* of preallocated items (which happens frequently).
*/
/*
* Allocate or release as necessary to meet our target pool size.
*/
static int __fill_msgpool(struct ceph_msgpool *pool)
{
struct ceph_msg *msg;
while (pool->num < pool->min) {
dout("fill_msgpool %p %d/%d allocating\n", pool, pool->num,
pool->min);
spin_unlock(&pool->lock);
msg = ceph_msg_new(0, pool->front_len, 0, 0, NULL);
spin_lock(&pool->lock);
if (IS_ERR(msg))
return PTR_ERR(msg);
msg->pool = pool;
list_add(&msg->list_head, &pool->msgs);
pool->num++;
}
while (pool->num > pool->min) {
msg = list_first_entry(&pool->msgs, struct ceph_msg, list_head);
dout("fill_msgpool %p %d/%d releasing %p\n", pool, pool->num,
pool->min, msg);
list_del_init(&msg->list_head);
pool->num--;
ceph_msg_kfree(msg);
}
return 0;
}
int ceph_msgpool_init(struct ceph_msgpool *pool,
int front_len, int min, bool blocking)
{
int ret;
dout("msgpool_init %p front_len %d min %d\n", pool, front_len, min);
spin_lock_init(&pool->lock);
pool->front_len = front_len;
INIT_LIST_HEAD(&pool->msgs);
pool->num = 0;
pool->min = min;
pool->blocking = blocking;
init_waitqueue_head(&pool->wait);
spin_lock(&pool->lock);
ret = __fill_msgpool(pool);
spin_unlock(&pool->lock);
return ret;
}
void ceph_msgpool_destroy(struct ceph_msgpool *pool)
{
dout("msgpool_destroy %p\n", pool);
spin_lock(&pool->lock);
pool->min = 0;
__fill_msgpool(pool);
spin_unlock(&pool->lock);
}
int ceph_msgpool_resv(struct ceph_msgpool *pool, int delta)
{
int ret;
spin_lock(&pool->lock);
dout("msgpool_resv %p delta %d\n", pool, delta);
pool->min += delta;
ret = __fill_msgpool(pool);
spin_unlock(&pool->lock);
return ret;
}
struct ceph_msg *ceph_msgpool_get(struct ceph_msgpool *pool)
{
wait_queue_t wait;
struct ceph_msg *msg;
if (pool->blocking) {
/* mempool_t behavior; first try to alloc */
msg = ceph_msg_new(0, pool->front_len, 0, 0, NULL);
if (!IS_ERR(msg))
return msg;
}
while (1) {
spin_lock(&pool->lock);
if (likely(pool->num)) {
msg = list_entry(pool->msgs.next, struct ceph_msg,
list_head);
list_del_init(&msg->list_head);
pool->num--;
dout("msgpool_get %p got %p, now %d/%d\n", pool, msg,
pool->num, pool->min);
spin_unlock(&pool->lock);
return msg;
}
pr_err("msgpool_get %p now %d/%d, %s\n", pool, pool->num,
pool->min, pool->blocking ? "waiting" : "failing");
spin_unlock(&pool->lock);
if (!pool->blocking) {
WARN_ON(1);
/* maybe we can allocate it now? */
msg = ceph_msg_new(0, pool->front_len, 0, 0, NULL);
if (!IS_ERR(msg))
return msg;
return ERR_PTR(-ENOMEM);
}
init_wait(&wait);
prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
schedule();
finish_wait(&pool->wait, &wait);
}
}
void ceph_msgpool_put(struct ceph_msgpool *pool, struct ceph_msg *msg)
{
spin_lock(&pool->lock);
if (pool->num < pool->min) {
ceph_msg_get(msg); /* retake a single ref */
list_add(&msg->list_head, &pool->msgs);
pool->num++;
dout("msgpool_put %p reclaim %p, now %d/%d\n", pool, msg,
pool->num, pool->min);
spin_unlock(&pool->lock);
wake_up(&pool->wait);
} else {
dout("msgpool_put %p drop %p, at %d/%d\n", pool, msg,
pool->num, pool->min);
spin_unlock(&pool->lock);
ceph_msg_kfree(msg);
}
}
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