--- mm/readahead.c

+++ mm/readahead.c

@@ -18,6 +18,32 @@

#include <linux/pagevec.h>

#include <linux/pagemap.h>

+unsigned long max_readahead_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE;

+

+static int __init readahead(char *str)

+{

+ unsigned long bytes;

+

+ if (!str)

+ return -EINVAL;

+ bytes = memparse(str, &str);

+ if (*str != '\0')

+ return -EINVAL;

+

+ if (bytes) {

+ if (bytes < PAGE_CACHE_SIZE) /* missed 'k'/'m' suffixes? */

+ return -EINVAL;

+ if (bytes > 256 << 20) /* limit to 256MB */

+ bytes = 256 << 20;

+ }

+

+ max_readahead_pages = bytes / PAGE_CACHE_SIZE;

+ default_backing_dev_info.ra_pages = max_readahead_pages;

+ return 0;

+}

+

+early_param("readahead", readahead);

+

/*

* Initialise a struct file's readahead state. Assumes that the caller has

* memset *ra to zero.