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>

3 files changed, 13 insertions, 19 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index fad9298c6962..0636f79672e9 100644
--- 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 ea6ee68ef53c..7ef3397a266d 100644
--- 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 4ef8bdd68348..d74a2b3e3b5d 100644
--- 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,