ceph: support ceph_pagelist for message payload
The ceph_pagelist is a simple list of whole pages, strung together via
their lru list_head. It facilitates encoding to a "buffer" of unknown
size. Allow its use in place of the ceph_msg page vector.
This will be used to fix the huge buffer preallocation woes of MDS
reconnection.
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/pagelist.c b/fs/ceph/pagelist.c
new file mode 100644
index 0000000..370e936
--- /dev/null
+++ b/fs/ceph/pagelist.c
@@ -0,0 +1,54 @@
+
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+
+#include "pagelist.h"
+
+int ceph_pagelist_release(struct ceph_pagelist *pl)
+{
+ if (pl->mapped_tail)
+ kunmap(pl->mapped_tail);
+ while (!list_empty(&pl->head)) {
+ struct page *page = list_first_entry(&pl->head, struct page,
+ lru);
+ list_del(&page->lru);
+ __free_page(page);
+ }
+ return 0;
+}
+
+static int ceph_pagelist_addpage(struct ceph_pagelist *pl)
+{
+ struct page *page = alloc_page(GFP_NOFS);
+ if (!page)
+ return -ENOMEM;
+ pl->room += PAGE_SIZE;
+ list_add_tail(&page->lru, &pl->head);
+ if (pl->mapped_tail)
+ kunmap(pl->mapped_tail);
+ pl->mapped_tail = kmap(page);
+ return 0;
+}
+
+int ceph_pagelist_append(struct ceph_pagelist *pl, void *buf, size_t len)
+{
+ while (pl->room < len) {
+ size_t bit = pl->room;
+ int ret;
+
+ memcpy(pl->mapped_tail + (pl->length & ~PAGE_CACHE_MASK),
+ buf, bit);
+ pl->length += bit;
+ pl->room -= bit;
+ buf += bit;
+ len -= bit;
+ ret = ceph_pagelist_addpage(pl);
+ if (ret)
+ return ret;
+ }
+
+ memcpy(pl->mapped_tail + (pl->length & ~PAGE_CACHE_MASK), buf, len);
+ pl->length += len;
+ pl->room -= len;
+ return 0;
+}