ceph: message pools

The msgpool is a basic mempool_t-like structure to preallocate
messages we expect to receive over the wire.  This ensures we have the
necessary memory preallocated to process replies to requests, or to
process unsolicited messages from various servers.

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

1 files changed, 26 insertions, 0 deletions

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