Btrfs: Use an array of pages in the extent buffers to reduce the cost of find_get_page

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index fad9298c696274c93612ac414d412aac76be289e..0636f79672e9ad409aa0702782ff9f95c32e7fbe 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -647,20 +647,20 @@ int close_ctree(struct btrfs_root *root)
 
 int btrfs_buffer_uptodate(struct extent_buffer *buf)
 {
-       struct inode *btree_inode = buf->first_page->mapping->host;
+       struct inode *btree_inode = buf->pages[0]->mapping->host;
        return extent_buffer_uptodate(&BTRFS_I(btree_inode)->extent_tree, buf);
 }
 
 int btrfs_set_buffer_uptodate(struct extent_buffer *buf)
 {
-       struct inode *btree_inode = buf->first_page->mapping->host;
+       struct inode *btree_inode = buf->pages[0]->mapping->host;
        return set_extent_buffer_uptodate(&BTRFS_I(btree_inode)->extent_tree,
                                          buf);
 }
 
 void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
 {
-       struct btrfs_root *root = BTRFS_I(buf->first_page->mapping->host)->root;
+       struct btrfs_root *root = BTRFS_I(buf->pages[0]->mapping->host)->root;
        u64 transid = btrfs_header_generation(buf);
        struct inode *btree_inode = root->fs_info->btree_inode;
 

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index ea6ee68ef53c6a55642213e59d7805c45ac88bf2..7ef3397a266d43628fc5de7123ca45ab391e03d7 100644 (file)
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -1961,16 +1961,12 @@ static void __free_extent_buffer(struct extent_buffer *eb)
 static inline struct page *extent_buffer_page(struct extent_buffer *eb, int i)
 {
        struct page *p;
-       if (i == 0)
-               return eb->first_page;
 
+       if (i < EXTENT_INLINE_PAGES)
+               return eb->pages[i];
        i += eb->start >> PAGE_CACHE_SHIFT;
-       if (eb->last_page && eb->last_page->index == i)
-               return eb->last_page;
-
-       p = find_get_page(eb->first_page->mapping, i);
+       p = find_get_page(eb->pages[0]->mapping, i);
        page_cache_release(p);
-       eb->last_page = p;
        return p;
 }
 
@@ -2012,8 +2008,8 @@ struct extent_buffer *alloc_extent_buffer(struct extent_map_tree *tree,
                        goto fail;
                }
                set_page_extent_mapped(p);
-               if (i == 0)
-                       eb->first_page = p;
+               if (i < EXTENT_INLINE_PAGES)
+                       eb->pages[i] = p;
                if (!PageUptodate(p))
                        uptodate = 0;
                unlock_page(p);
@@ -2059,8 +2055,8 @@ struct extent_buffer *find_extent_buffer(struct extent_map_tree *tree,
                        goto fail;
                }
                set_page_extent_mapped(p);
-               if (i == 0)
-                       eb->first_page = p;
+               if (i < EXTENT_INLINE_PAGES)
+                       eb->pages[i] = p;
                if (!PageUptodate(p))
                        uptodate = 0;
                unlock_page(p);
@@ -2087,9 +2083,7 @@ void free_extent_buffer(struct extent_buffer *eb)
 
        num_pages = num_extent_pages(eb->start, eb->len);
 
-       if (eb->first_page)
-               page_cache_release(eb->first_page);
-       for (i = 1; i < num_pages; i++) {
+       for (i = 0; i < num_pages; i++) {
                page_cache_release(extent_buffer_page(eb, i));
        }
        __free_extent_buffer(eb);

diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
index 4ef8bdd68348a058162fd2136413d1694b8bfa14..d74a2b3e3b5dd3271ed2df7e3eec2e8b2619d2a3 100644 (file)
--- a/fs/btrfs/extent_map.h
+++ b/fs/btrfs/extent_map.h
@@ -62,6 +62,7 @@ struct extent_state {
        struct list_head list;
 };
 
+#define EXTENT_INLINE_PAGES 32
 struct extent_buffer {
        u64 start;
        unsigned long len;
@@ -69,13 +70,12 @@ struct extent_buffer {
        int flags;
        struct list_head list;
        struct list_head leak_list;
-       struct page *first_page;
-       struct page *last_page;
        unsigned long alloc_addr;
        char *map_token;
        char *kaddr;
        unsigned long map_start;
        unsigned long map_len;
+       struct page *pages[EXTENT_INLINE_PAGES];
 };
 
 typedef struct extent_map *(get_extent_t)(struct inode *inode,