diff --git a/fs/ceph/msgpool.c b/fs/ceph/msgpool.c
new file mode 100644
index 000000000000..39d4d7ed82ce
--- /dev/null
+++ b/fs/ceph/msgpool.c
@@ -0,0 +1,167 @@
+#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);
+	}
+}
diff --git a/fs/ceph/msgpool.h b/fs/ceph/msgpool.h
new file mode 100644
index 000000000000..07a2decaa6d8
--- /dev/null
+++ b/fs/ceph/msgpool.h
@@ -0,0 +1,26 @@
+#ifndef _FS_CEPH_MSGPOOL
+#define _FS_CEPH_MSGPOOL
+
+#include "messenger.h"
+
+/*
+ * we use memory pools for preallocating messages we may receive, to
+ * avoid unexpected OOM conditions.
+ */
+struct ceph_msgpool {
+	spinlock_t lock;
+	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 *);
+extern void ceph_msgpool_put(struct ceph_msgpool *, struct ceph_msg *);
+
+#endif