X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=include%2Flinux%2Fbuffer_head.h;h=5d9fb0e94156235eca46e199352933fc638b9596;hb=refs%2Fheads%2Fvserver;hp=9f159baf153fbcc12a4c7889d92597e35d205391;hpb=76828883507a47dae78837ab5dec5a5b4513c667;p=linux-2.6.git

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 9f159baf1..5d9fb0e94 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -14,6 +14,8 @@
 #include <linux/wait.h>
 #include <asm/atomic.h>
 
+#ifdef CONFIG_BLOCK
+
 enum bh_state_bits {
 	BH_Uptodate,	/* Contains valid data */
 	BH_Dirty,	/* Is dirty */
@@ -46,25 +48,30 @@ struct address_space;
 typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
 
 /*
- * Keep related fields in common cachelines.  The most commonly accessed
- * field (b_state) goes at the start so the compiler does not generate
- * indexed addressing for it.
+ * Historically, a buffer_head was used to map a single block
+ * within a page, and of course as the unit of I/O through the
+ * filesystem and block layers.  Nowadays the basic I/O unit
+ * is the bio, and buffer_heads are used for extracting block
+ * mappings (via a get_block_t call), for tracking state within
+ * a page (via a page_mapping) and for wrapping bio submission
+ * for backward compatibility reasons (e.g. submit_bh).
  */
 struct buffer_head {
-	/* First cache line: */
 	unsigned long b_state;		/* buffer state bitmap (see above) */
 	struct buffer_head *b_this_page;/* circular list of page's buffers */
 	struct page *b_page;		/* the page this bh is mapped to */
-	atomic_t b_count;		/* users using this block */
-	u32 b_size;			/* block size */
 
-	sector_t b_blocknr;		/* block number */
-	char *b_data;			/* pointer to data block */
+	sector_t b_blocknr;		/* start block number */
+	size_t b_size;			/* size of mapping */
+	char *b_data;			/* pointer to data within the page */
 
 	struct block_device *b_bdev;
 	bh_end_io_t *b_end_io;		/* I/O completion */
  	void *b_private;		/* reserved for b_end_io */
 	struct list_head b_assoc_buffers; /* associated with another mapping */
+	struct address_space *b_assoc_map;	/* mapping this buffer is
+						   associated with */
+	atomic_t b_count;		/* users using this buffer_head */
 };
 
 /*
@@ -146,7 +153,6 @@ void create_empty_buffers(struct page *, unsigned long,
 			unsigned long b_state);
 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
-void end_buffer_async_write(struct buffer_head *bh, int uptodate);
 
 /* Things to do with buffers at mapping->private_list */
 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode);
@@ -188,9 +194,7 @@ extern int buffer_heads_over_limit;
  * Generic address_space_operations implementations for buffer_head-backed
  * address_spaces.
  */
-int try_to_release_page(struct page * page, gfp_t gfp_mask);
-int block_invalidatepage(struct page *page, unsigned long offset);
-int do_invalidatepage(struct page *page, unsigned long offset);
+void block_invalidatepage(struct page *page, unsigned long offset);
 int block_write_full_page(struct page *page, get_block_t *get_block,
 				struct writeback_control *wbc);
 int block_read_full_page(struct page*, get_block_t*);
@@ -200,7 +204,7 @@ int cont_prepare_write(struct page*, unsigned, unsigned, get_block_t*,
 int generic_cont_expand(struct inode *inode, loff_t size);
 int generic_cont_expand_simple(struct inode *inode, loff_t size);
 int block_commit_write(struct page *page, unsigned from, unsigned to);
-int block_sync_page(struct page *);
+void block_sync_page(struct page *);
 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 int generic_commit_write(struct file *, struct page *, unsigned, unsigned);
 int block_truncate_page(struct address_space *, loff_t, get_block_t *);
@@ -211,6 +215,7 @@ int nobh_truncate_page(struct address_space *, loff_t);
 int nobh_writepage(struct page *page, get_block_t *get_block,
                         struct writeback_control *wbc);
 
+void buffer_init(void);
 
 /*
  * inline definitions
@@ -277,6 +282,7 @@ map_bh(struct buffer_head *bh, struct super_block *sb, sector_t block)
 	set_buffer_mapped(bh);
 	bh->b_bdev = sb->s_bdev;
 	bh->b_blocknr = block;
+	bh->b_size = sb->s_blocksize;
 }
 
 /*
@@ -298,4 +304,19 @@ static inline void lock_buffer(struct buffer_head *bh)
 		__lock_buffer(bh);
 }
 
+extern int __set_page_dirty_buffers(struct page *page);
+
+#else /* CONFIG_BLOCK */
+
+static inline void buffer_init(void) {}
+static inline int try_to_free_buffers(struct page *page) { return 1; }
+static inline int sync_blockdev(struct block_device *bdev) { return 0; }
+static inline int inode_has_buffers(struct inode *inode) { return 0; }
+static inline void invalidate_inode_buffers(struct inode *inode) {}
+static inline int remove_inode_buffers(struct inode *inode) { return 1; }
+static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }
+static inline void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers) {}
+
+
+#endif /* CONFIG_BLOCK */
 #endif /* _LINUX_BUFFER_HEAD_H */