libceph: implement pages array cursor

Implement and use cursor routines for page array message data items
for outbound message data.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

1 files changed, 89 insertions, 4 deletions

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 209990a853e5..d611156808b3 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -831,6 +831,79 @@ static bool ceph_msg_data_bio_advance(struct ceph_msg_data *data, size_t bytes)
 #endif
 
 /*
+ * For a page array, a piece comes from the first page in the array
+ * that has not already been fully consumed.
+ */
+static void ceph_msg_data_pages_cursor_init(struct ceph_msg_data *data)
+{
+        struct ceph_msg_data_cursor *cursor = &data->cursor;
+        int page_count;
+
+        BUG_ON(data->type != CEPH_MSG_DATA_PAGES);
+
+        BUG_ON(!data->pages);
+        BUG_ON(!data->length);
+
+        page_count = calc_pages_for(data->alignment, (u64)data->length);
+        BUG_ON(page_count > (int) USHRT_MAX);
+        cursor->resid = data->length;
+        cursor->page_offset = data->alignment & ~PAGE_MASK;
+        cursor->page_index = 0;
+        cursor->page_count = (unsigned short) page_count;
+        cursor->last_piece = cursor->page_count == 1;
+}
+
+static struct page *ceph_msg_data_pages_next(struct ceph_msg_data *data,
+                                        size_t *page_offset,
+                                        size_t *length)
+{
+        struct ceph_msg_data_cursor *cursor = &data->cursor;
+
+        BUG_ON(data->type != CEPH_MSG_DATA_PAGES);
+
+        BUG_ON(cursor->page_index >= cursor->page_count);
+        BUG_ON(cursor->page_offset >= PAGE_SIZE);
+        BUG_ON(!cursor->resid);
+
+        *page_offset = cursor->page_offset;
+        if (cursor->last_piece) {
+                BUG_ON(*page_offset + cursor->resid > PAGE_SIZE);
+                *length = cursor->resid;
+        } else {
+                *length = PAGE_SIZE - *page_offset;
+        }
+
+        return data->pages[cursor->page_index];
+}
+
+static bool ceph_msg_data_pages_advance(struct ceph_msg_data *data,
+                                                size_t bytes)
+{
+        struct ceph_msg_data_cursor *cursor = &data->cursor;
+
+        BUG_ON(data->type != CEPH_MSG_DATA_PAGES);
+
+        BUG_ON(cursor->page_offset + bytes > PAGE_SIZE);
+        BUG_ON(bytes > cursor->resid);
+
+        /* Advance the cursor page offset */
+
+        cursor->resid -= bytes;
+        cursor->page_offset += bytes;
+        if (!bytes || cursor->page_offset & ~PAGE_MASK)
+                return false;   /* more bytes to process in the current page */
+
+        /* Move on to the next page */
+
+        BUG_ON(cursor->page_index >= cursor->page_count);
+        cursor->page_offset = 0;
+        cursor->page_index++;
+        cursor->last_piece = cursor->page_index == cursor->page_count - 1;
+
+        return true;
+}
+
+/*
  * For a pagelist, a piece is whatever remains to be consumed in the
  * first page in the list, or the front of the next page.
  */
@@ -932,13 +1005,15 @@ static void ceph_msg_data_cursor_init(struct ceph_msg_data *data)
         case CEPH_MSG_DATA_PAGELIST:
                 ceph_msg_data_pagelist_cursor_init(data);
                 break;
+        case CEPH_MSG_DATA_PAGES:
+                ceph_msg_data_pages_cursor_init(data);
+                break;
 #ifdef CONFIG_BLOCK
         case CEPH_MSG_DATA_BIO:
                 ceph_msg_data_bio_cursor_init(data);
                 break;
 #endif /* CONFIG_BLOCK */
         case CEPH_MSG_DATA_NONE:
-        case CEPH_MSG_DATA_PAGES:
         default:
                 /* BUG(); */
                 break;
@@ -961,13 +1036,15 @@ static struct page *ceph_msg_data_next(struct ceph_msg_data *data,
         case CEPH_MSG_DATA_PAGELIST:
                 page = ceph_msg_data_pagelist_next(data, page_offset, length);
                 break;
+        case CEPH_MSG_DATA_PAGES:
+                page = ceph_msg_data_pages_next(data, page_offset, length);
+                break;
 #ifdef CONFIG_BLOCK
         case CEPH_MSG_DATA_BIO:
                 page = ceph_msg_data_bio_next(data, page_offset, length);
                 break;
 #endif /* CONFIG_BLOCK */
         case CEPH_MSG_DATA_NONE:
-        case CEPH_MSG_DATA_PAGES:
         default:
                 page = NULL;
                 break;
@@ -993,13 +1070,15 @@ static bool ceph_msg_data_advance(struct ceph_msg_data *data, size_t bytes)
         case CEPH_MSG_DATA_PAGELIST:
                 new_piece = ceph_msg_data_pagelist_advance(data, bytes);
                 break;
+        case CEPH_MSG_DATA_PAGES:
+                new_piece = ceph_msg_data_pages_advance(data, bytes);
+                break;
 #ifdef CONFIG_BLOCK
         case CEPH_MSG_DATA_BIO:
                 new_piece = ceph_msg_data_bio_advance(data, bytes);
                 break;
 #endif /* CONFIG_BLOCK */
         case CEPH_MSG_DATA_NONE:
-        case CEPH_MSG_DATA_PAGES:
         default:
                 BUG();
                 break;
@@ -1032,6 +1111,8 @@ static void prepare_message_data(struct ceph_msg *msg,
         if (ceph_msg_has_bio(msg))
                 ceph_msg_data_cursor_init(&msg->b);
 #endif /* CONFIG_BLOCK */
+        if (ceph_msg_has_pages(msg))
+                ceph_msg_data_cursor_init(&msg->p);
         if (ceph_msg_has_pagelist(msg))
                 ceph_msg_data_cursor_init(&msg->l);
         if (ceph_msg_has_trail(msg))
@@ -1330,6 +1411,8 @@ static void out_msg_pos_next(struct ceph_connection *con, struct page *page,
         msg_pos->page_pos += sent;
         if (in_trail)
                 need_crc = ceph_msg_data_advance(&msg->t, sent);
+        else if (ceph_msg_has_pages(msg))
+                need_crc = ceph_msg_data_advance(&msg->p, sent);
         else if (ceph_msg_has_pagelist(msg))
                 need_crc = ceph_msg_data_advance(&msg->l, sent);
 #ifdef CONFIG_BLOCK
@@ -1435,7 +1518,9 @@ static int write_partial_message_data(struct ceph_connection *con)
                         page = ceph_msg_data_next(&msg->t, &page_offset,
                                                         &length, &last_piece);
                 } else if (ceph_msg_has_pages(msg)) {
-                        page = msg->p.pages[msg_pos->page];
+                        use_cursor = true;
+                        page = ceph_msg_data_next(&msg->p, &page_offset,
+                                                        &length, &last_piece);
                 } else if (ceph_msg_has_pagelist(msg)) {
                         use_cursor = true;
                         page = ceph_msg_data_next(&msg->l, &page_offset,