[PATCH] add page_offset to mm.h

[Christoph Hellwig <hch@lst.de>]

To convert page->index to a byte index you need to cast it to loff_t
first so it's a 64bit value.  There have been quite a few places that
got it wrong in the kernel.  To make it easier a nice little helper
would be nice, and in fact the NFS code already has it.  Let's move it
to pagemap.h so everyone can use it.


--- 1.92/include/linux/nfs_fs.h	2005-01-04 01:00:00 +01:00
+++ edited/include/linux/nfs_fs.h	2005-01-19 11:40:42 +01:00
@@ -254,12 +254,6 @@
 	return NFS_FLAGS(inode) & NFS_INO_ADVISE_RDPLUS;
 }
 
-static inline
-loff_t page_offset(struct page *page)
-{
-	return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
-}
-
 /**
  * nfs_save_change_attribute - Returns the inode attribute change cookie
  * @inode - pointer to inode
--- 1.44/include/linux/pagemap.h	2004-08-27 08:31:38 +02:00
+++ edited/include/linux/pagemap.h	2005-01-19 11:42:59 +01:00
@@ -143,6 +143,14 @@
 	return ret;
 }
 
+/*
+ * Return byte-offset into filesystem object for page.
+ */
+static inline loff_t page_offset(struct page *page)
+{
+	return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
+}
+
 static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
 					unsigned long address)
 {