commit f4e6b498d6e06742d72706ef50593a9c4dd72214
author Fengguang Wu <wfg@mail.ustc.edu.cn> Tue Oct 16 01:24:33 2007 -0700
committer Linus Torvalds <torvalds@woody.linux-foundation.org> Tue Oct 16 09:42:52 2007 -0700
tree 74a573302b2ea086c0d21907175be604f110f5b1
parent 0bb7ba6b9c358c12084a3cbc6ac08c8d1e973937

readahead: combine file_ra_state.prev_index/prev_offset into prev_pos

Combine the file_ra_state members
				unsigned long prev_index
				unsigned int prev_offset
into
				loff_t prev_pos

It is more consistent and better supports huge files.

Thanks to Peter for the nice proposal!

[akpm@linux-foundation.org: fix shift overflow]
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/filemap.c

diff --git a/mm/filemap.c b/mm/filemap.c
index 5dc18d7..bbcca45 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -879,8 +879,8 @@
 	cached_page = NULL;
 	index = *ppos >> PAGE_CACHE_SHIFT;
 	next_index = index;
-	prev_index = ra.prev_index;
-	prev_offset = ra.prev_offset;
+	prev_index = ra.prev_pos >> PAGE_CACHE_SHIFT;
+	prev_offset = ra.prev_pos & (PAGE_CACHE_SIZE-1);
 	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 	offset = *ppos & ~PAGE_CACHE_MASK;
 
@@ -966,7 +966,6 @@
 		index += offset >> PAGE_CACHE_SHIFT;
 		offset &= ~PAGE_CACHE_MASK;
 		prev_offset = offset;
-		ra.prev_offset = offset;
 
 		page_cache_release(page);
 		if (ret == nr && desc->count)
@@ -1056,9 +1055,11 @@
 
 out:
 	*_ra = ra;
-	_ra->prev_index = prev_index;
+	_ra->prev_pos = prev_index;
+	_ra->prev_pos <<= PAGE_CACHE_SHIFT;
+	_ra->prev_pos |= prev_offset;
 
-	*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
+	*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
 	if (cached_page)
 		page_cache_release(cached_page);
 	if (filp)
@@ -1396,7 +1397,7 @@
 	 * Found the page and have a reference on it.
 	 */
 	mark_page_accessed(page);
-	ra->prev_index = page->index;
+	ra->prev_pos = (loff_t)page->index << PAGE_CACHE_SHIFT;
 	vmf->page = page;
 	return ret | VM_FAULT_LOCKED;