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>

5 files changed, 130 insertions, 5 deletions

diff --git a/fs/ceph/Makefile b/fs/ceph/Makefile
index 827629c85768..47caf2f1b75a 100644
--- a/fs/ceph/Makefile
+++ b/fs/ceph/Makefile
@@ -8,7 +8,7 @@ obj-$(CONFIG_CEPH_FS) += ceph.o
 
 ceph-objs := super.o inode.o dir.o file.o addr.o ioctl.o \
         export.o caps.o snap.o xattr.o \
-        messenger.o msgpool.o buffer.o \
+        messenger.o msgpool.o buffer.o pagelist.o \
         mds_client.o mdsmap.o \
         mon_client.o \
         osd_client.o osdmap.o crush/crush.o crush/mapper.o crush/hash.o \
diff --git a/fs/ceph/messenger.c b/fs/ceph/messenger.c
index 68052f664280..c1106e8360f0 100644
--- a/fs/ceph/messenger.c
+++ b/fs/ceph/messenger.c
@@ -13,6 +13,7 @@
 #include "super.h"
 #include "messenger.h"
 #include "decode.h"
+#include "pagelist.h"
 
 /*
  * Ceph uses the messenger to exchange ceph_msg messages with other
@@ -728,6 +729,11 @@ static int write_partial_msg_pages(struct ceph_connection *con)
                         page = msg->pages[con->out_msg_pos.page];
                         if (crc)
                                 kaddr = kmap(page);
+                } else if (msg->pagelist) {
+                        page = list_first_entry(&msg->pagelist->head,
+                                                struct page, lru);
+                        if (crc)
+                                kaddr = kmap(page);
                 } else {
                         page = con->msgr->zero_page;
                         if (crc)
@@ -750,7 +756,7 @@ static int write_partial_msg_pages(struct ceph_connection *con)
                                       MSG_DONTWAIT | MSG_NOSIGNAL |
                                       MSG_MORE);
 
-                if (crc && msg->pages)
+                if (crc && (msg->pages || msg->pagelist))
                         kunmap(page);
 
                 if (ret <= 0)
@@ -762,6 +768,9 @@ static int write_partial_msg_pages(struct ceph_connection *con)
                         con->out_msg_pos.page_pos = 0;
                         con->out_msg_pos.page++;
                         con->out_msg_pos.did_page_crc = 0;
+                        if (msg->pagelist)
+                                list_move_tail(&page->lru,
+                                               &msg->pagelist->head);
                 }
         }
 
@@ -1051,13 +1060,13 @@ static int process_banner(struct ceph_connection *con)
                                        &con->actual_peer_addr) &&
             !(addr_is_blank(&con->actual_peer_addr.in_addr) &&
               con->actual_peer_addr.nonce == con->peer_addr.nonce)) {
-                pr_err("wrong peer, want %s/%d, "
-                       "got %s/%d, wtf\n",
+                pr_warning("wrong peer, want %s/%d, "
+                       "got %s/%d\n",
                        pr_addr(&con->peer_addr.in_addr),
                        con->peer_addr.nonce,
                        pr_addr(&con->actual_peer_addr.in_addr),
                        con->actual_peer_addr.nonce);
-                con->error_msg = "protocol error, wrong peer";
+                con->error_msg = "wrong peer at address";
                 return -1;
         }
 
@@ -2096,6 +2105,7 @@ struct ceph_msg *ceph_msg_new(int type, int front_len,
         /* data */
         m->nr_pages = calc_pages_for(page_off, page_len);
         m->pages = pages;
+        m->pagelist = NULL;
 
         dout("ceph_msg_new %p page %d~%d -> %d\n", m, page_off, page_len,
              m->nr_pages);
@@ -2181,6 +2191,12 @@ void ceph_msg_last_put(struct kref *kref)
         m->nr_pages = 0;
         m->pages = NULL;
 
+        if (m->pagelist) {
+                ceph_pagelist_release(m->pagelist);
+                kfree(m->pagelist);
+                m->pagelist = NULL;
+        }
+
         if (m->pool)
                 ceph_msgpool_put(m->pool, m);
         else
diff --git a/fs/ceph/messenger.h b/fs/ceph/messenger.h
index 7e2aab1d3ce2..a7b684145092 100644
--- a/fs/ceph/messenger.h
+++ b/fs/ceph/messenger.h
@@ -85,6 +85,7 @@ struct ceph_msg {
         struct ceph_buffer *middle;
         struct page **pages;            /* data payload.  NOT OWNER. */
         unsigned nr_pages;              /* size of page array */
+        struct ceph_pagelist *pagelist; /* instead of pages */
         struct list_head list_head;
         struct kref kref;
         bool front_is_vmalloc;
diff --git a/fs/ceph/pagelist.c b/fs/ceph/pagelist.c
new file mode 100644
index 000000000000..370e93695474
--- /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;
+}
diff --git a/fs/ceph/pagelist.h b/fs/ceph/pagelist.h
new file mode 100644
index 000000000000..e8a4187e1087
--- /dev/null
+++ b/fs/ceph/pagelist.h
@@ -0,0 +1,54 @@
+#ifndef __FS_CEPH_PAGELIST_H
+#define __FS_CEPH_PAGELIST_H
+
+#include <linux/list.h>
+
+struct ceph_pagelist {
+        struct list_head head;
+        void *mapped_tail;
+        size_t length;
+        size_t room;
+};
+
+static inline void ceph_pagelist_init(struct ceph_pagelist *pl)
+{
+        INIT_LIST_HEAD(&pl->head);
+        pl->mapped_tail = NULL;
+        pl->length = 0;
+        pl->room = 0;
+}
+extern int ceph_pagelist_release(struct ceph_pagelist *pl);
+
+extern int ceph_pagelist_append(struct ceph_pagelist *pl, void *d, size_t l);
+
+static inline int ceph_pagelist_encode_64(struct ceph_pagelist *pl, u64 v)
+{
+        __le64 ev = cpu_to_le64(v);
+        return ceph_pagelist_append(pl, &ev, sizeof(ev));
+}
+static inline int ceph_pagelist_encode_32(struct ceph_pagelist *pl, u32 v)
+{
+        __le32 ev = cpu_to_le32(v);
+        return ceph_pagelist_append(pl, &ev, sizeof(ev));
+}
+static inline int ceph_pagelist_encode_16(struct ceph_pagelist *pl, u16 v)
+{
+        __le16 ev = cpu_to_le16(v);
+        return ceph_pagelist_append(pl, &ev, sizeof(ev));
+}
+static inline int ceph_pagelist_encode_8(struct ceph_pagelist *pl, u8 v)
+{
+        return ceph_pagelist_append(pl, &v, 1);
+}
+static inline int ceph_pagelist_encode_string(struct ceph_pagelist *pl,
+                                              char *s, size_t len)
+{
+        int ret = ceph_pagelist_encode_32(pl, len);
+        if (ret)
+                return ret;
+        if (len)
+                return ceph_pagelist_append(pl, s, len);
+        return 0;
+}
+
+#endif