From 4073a4679c09ba3ea4b2c4dbe5948998fecbaef7 Mon Sep 17 00:00:00 2001
From: Sage Weil <sage@newdream.net>
Date: Thu, 16 Jul 2009 15:40:57 -0700
Subject: [PATCH] kclient: file.c cleanup

---
 src/kernel/file.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/kernel/file.c b/src/kernel/file.c
index 71f8017c499fb..1af59c0f655e7 100644
--- a/src/kernel/file.c
+++ b/src/kernel/file.c
@@ -8,6 +8,27 @@
 #include "super.h"
 #include "mds_client.h"
 
+/*
+ * Ceph file operations
+ *
+ * Implement basic open/close functionality, and implement
+ * read/write.
+ *
+ * We implement three modes of file I/O:
+ *  - buffered uses the generic_file_aio_{read,write} helpers
+ *
+ *  - synchronous is used when there is multi-client read/write
+ *    sharing, avoids the page cache, and synchronously waits for an
+ *    ack from the OSD.
+ *
+ *  - direct io takes the variant of the sync path that references
+ *    user pages directly.
+ *
+ * fsync() flushes and waits on dirty pages, but just queues metadata
+ * for writeback: since the MDS can recover size and mtime there is no
+ * need to wait for MDS acknowledgement.
+ */
+
 
 /*
  * Prepare an open request.  Preallocate ceph_cap to avoid an
@@ -288,6 +309,9 @@ void ceph_release_page_vector(struct page **pages, int num_pages)
 	kfree(pages);
 }
 
+/*
+ * allocate a vector new pages
+ */
 static struct page **alloc_page_vector(int num_pages)
 {
 	struct page **pages;
-- 
2.39.5