ceph: rewrite msgpool using mempool_t

Since we don't need to maintain large pools of messages, we can just
use the standard mempool_t.  We maintain a msgpool 'wrapper' because we
need the mempool_t* in the alloc function, and mempool gives us only
pool_data.

Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/fs/ceph/msgpool.c b/fs/ceph/msgpool.c
index 030297f..ca03222 100644 (file)
--- a/fs/ceph/msgpool.c
+++ b/fs/ceph/msgpool.c
@@ -7,106 +7,43 @@
 
 #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).
- */
+static void *alloc_fn(gfp_t gfp_mask, void *arg)
+{
+       struct ceph_msgpool *pool = arg;
+       struct ceph_msg *m;
 
+       m = ceph_msg_new(0, pool->front_len, 0, 0, NULL);
+       if (IS_ERR(m))
+               return NULL;
+       return m;
+}
 
-/*
- * Allocate or release as necessary to meet our target pool size.
- */
-static int __fill_msgpool(struct ceph_msgpool *pool)
+static void free_fn(void *element, void *arg)
 {
-       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;
+       ceph_msg_put(element);
 }
 
 int ceph_msgpool_init(struct ceph_msgpool *pool,
-                     int front_len, int min, bool blocking)
+                     int front_len, int size, 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;
+       pool->pool = mempool_create(size, alloc_fn, free_fn, pool);
+       if (!pool->pool)
+               return -ENOMEM;
+       return 0;
 }
 
 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;
+       mempool_destroy(pool->pool);
 }
 
-struct ceph_msg *ceph_msgpool_get(struct ceph_msgpool *pool, int front_len)
+struct ceph_msg *ceph_msgpool_get(struct ceph_msgpool *pool,
+                                 int front_len)
 {
-       wait_queue_t wait;
-       struct ceph_msg *msg;
+       if (front_len > pool->front_len) {
+               struct ceph_msg *msg;
 
-       if (front_len && front_len > pool->front_len) {
                pr_err("msgpool_get pool %p need front %d, pool size is %d\n",
                       pool, front_len, pool->front_len);
                WARN_ON(1);
@@ -115,72 +52,17 @@ struct ceph_msg *ceph_msgpool_get(struct ceph_msgpool *pool, int front_len)
                msg = ceph_msg_new(0, front_len, 0, 0, NULL);
                if (!IS_ERR(msg))
                        return msg;
+               return NULL;
        }
 
-       if (!front_len)
-               front_len = pool->front_len;
-
-       if (pool->blocking) {
-               /* mempool_t behavior; first try to alloc */
-               msg = ceph_msg_new(0, 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" : "may fail");
-               spin_unlock(&pool->lock);
-
-               if (!pool->blocking) {
-                       WARN_ON(1);
-
-                       /* maybe we can allocate it now? */
-                       msg = ceph_msg_new(0, front_len, 0, 0, NULL);
-                       if (!IS_ERR(msg))
-                               return msg;
-
-                       pr_err("msgpool_get %p empty + alloc failed\n", pool);
-                       return ERR_PTR(-ENOMEM);
-               }
-
-               init_wait(&wait);
-               prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
-               schedule();
-               finish_wait(&pool->wait, &wait);
-       }
+       return mempool_alloc(pool->pool, GFP_NOFS);
 }
 
 void ceph_msgpool_put(struct ceph_msgpool *pool, struct ceph_msg *msg)
 {
-       spin_lock(&pool->lock);
-       if (pool->num < pool->min) {
-               /* reset msg front_len; user may have changed it */
-               msg->front.iov_len = pool->front_len;
-               msg->hdr.front_len = cpu_to_le32(pool->front_len);
+       /* reset msg front_len; user may have changed it */
+       msg->front.iov_len = pool->front_len;
+       msg->hdr.front_len = cpu_to_le32(pool->front_len);
 
-               kref_init(&msg->kref);  /* 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);
-       }
+       kref_init(&msg->kref);  /* retake single ref */
 }

diff --git a/fs/ceph/msgpool.h b/fs/ceph/msgpool.h
index bc834bf..62a61c7 100644 (file)
--- a/fs/ceph/msgpool.h
+++ b/fs/ceph/msgpool.h
@@ -1,6 +1,7 @@
 #ifndef _FS_CEPH_MSGPOOL
 #define _FS_CEPH_MSGPOOL
 
+#include <linux/mempool.h>
 #include "messenger.h"
 
 /*
@@ -8,18 +9,13 @@
  * avoid unexpected OOM conditions.
  */
 struct ceph_msgpool {
-       spinlock_t lock;
+       mempool_t *pool;
        int front_len;          /* preallocated payload size */
-       struct list_head msgs;  /* msgs in the pool; each has 1 ref */
-       int num, min;           /* cur, min # msgs in the pool */
-       bool blocking;
-       wait_queue_head_t wait;
 };
 
 extern int ceph_msgpool_init(struct ceph_msgpool *pool,
                             int front_len, int size, bool blocking);
 extern void ceph_msgpool_destroy(struct ceph_msgpool *pool);
-extern int ceph_msgpool_resv(struct ceph_msgpool *, int delta);
 extern struct ceph_msg *ceph_msgpool_get(struct ceph_msgpool *,
                                         int front_len);
 extern void ceph_msgpool_put(struct ceph_msgpool *, struct ceph_msg *);