From 455c8d461c6daac02fc31376f435657c7e34b1b5 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Sun, 6 May 2007 14:49:25 -0700
Subject: [PATCH] --- yaml --- r: 54188 b: refs/heads/master c:
 ec0f16372277052a29a6c17527c6cae5e898b3fd h: refs/heads/master v: v3

---
 [refs]                   | 2 +-
 trunk/include/linux/fs.h | 1 +
 trunk/mm/filemap.c       | 9 ++++++---
 trunk/mm/readahead.c     | 3 +++
 4 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/[refs] b/[refs]
index c27e3a2c3b0f..a2fb0478d5b1 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b813e931b4c8235bb42e301096ea97dbdee3e8fe
+refs/heads/master: ec0f16372277052a29a6c17527c6cae5e898b3fd
diff --git a/trunk/include/linux/fs.h b/trunk/include/linux/fs.h
index 7c0077f06e24..0949e243b8b9 100644
--- a/trunk/include/linux/fs.h
+++ b/trunk/include/linux/fs.h
@@ -702,6 +702,7 @@ struct file_ra_state {
 	unsigned long ra_pages;		/* Maximum readahead window */
 	unsigned long mmap_hit;		/* Cache hit stat for mmap accesses */
 	unsigned long mmap_miss;	/* Cache miss stat for mmap accesses */
+	unsigned int offset;		/* Offset where last read() ended in a page */
 };
 #define RA_FLAG_MISS 0x01	/* a cache miss occured against this file */
 #define RA_FLAG_INCACHE 0x02	/* file is already in cache */
diff --git a/trunk/mm/filemap.c b/trunk/mm/filemap.c
index cbea95a25283..07f5b77114a3 100644
--- a/trunk/mm/filemap.c
+++ b/trunk/mm/filemap.c
@@ -868,6 +868,7 @@ void do_generic_mapping_read(struct address_space *mapping,
 	unsigned long last_index;
 	unsigned long next_index;
 	unsigned long prev_index;
+	unsigned int prev_offset;
 	loff_t isize;
 	struct page *cached_page;
 	int error;
@@ -877,6 +878,7 @@ void do_generic_mapping_read(struct address_space *mapping,
 	index = *ppos >> PAGE_CACHE_SHIFT;
 	next_index = index;
 	prev_index = ra.prev_page;
+	prev_offset = ra.offset;
 	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
 	offset = *ppos & ~PAGE_CACHE_MASK;
 
@@ -924,10 +926,10 @@ void do_generic_mapping_read(struct address_space *mapping,
 			flush_dcache_page(page);
 
 		/*
-		 * When (part of) the same page is read multiple times
-		 * in succession, only mark it as accessed the first time.
+		 * When a sequential read accesses a page several times,
+		 * only mark it as accessed the first time.
 		 */
-		if (prev_index != index)
+		if (prev_index != index || offset != prev_offset)
 			mark_page_accessed(page);
 		prev_index = index;
 
@@ -945,6 +947,7 @@ void do_generic_mapping_read(struct address_space *mapping,
 		offset += ret;
 		index += offset >> PAGE_CACHE_SHIFT;
 		offset &= ~PAGE_CACHE_MASK;
+		prev_offset = ra.offset = offset;
 
 		page_cache_release(page);
 		if (ret == nr && desc->count)
diff --git a/trunk/mm/readahead.c b/trunk/mm/readahead.c
index 93d9ee692fd8..0a6fed9d365c 100644
--- a/trunk/mm/readahead.c
+++ b/trunk/mm/readahead.c
@@ -207,6 +207,8 @@ static int read_pages(struct address_space *mapping, struct file *filp,
  *              If page_cache_readahead sees that it is again being called for
  *              a page which it just looked at, it can return immediately without
  *              making any state changes.
+ * offset:      Offset in the prev_page where the last read ended - used for
+ *              detection of sequential file reading.
  * ahead_start,
  * ahead_size:  Together, these form the "ahead window".
  * ra_pages:	The externally controlled max readahead for this fd.
@@ -473,6 +475,7 @@ page_cache_readahead(struct address_space *mapping, struct file_ra_state *ra,
 	/* Note that prev_page == -1 if it is a first read */
 	sequential = (offset == ra->prev_page + 1);
 	ra->prev_page = offset;
+	ra->offset = 0;
 
 	max = get_max_readahead(ra);
 	newsize = min(req_size, max);