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-rw-r--r--include/linux/fs.h1
-rw-r--r--mm/filemap.c9
-rw-r--r--mm/readahead.c3
3 files changed, 10 insertions, 3 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7c0077f06e2..0949e243b8b 100644
--- a/include/linux/fs.h
+++ b/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/mm/filemap.c b/mm/filemap.c
index cbea95a2528..07f5b77114a 100644
--- a/mm/filemap.c
+++ b/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 @@ page_ok:
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 @@ page_ok:
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/mm/readahead.c b/mm/readahead.c
index 93d9ee692fd..0a6fed9d365 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -207,6 +207,8 @@ out:
* 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);