From 5ce1110b92b31d079aa443e967f43a2294e01194 Mon Sep 17 00:00:00 2001
From: Fengguang Wu <wfg@mail.ustc.edu.cn>
Date: Thu, 19 Jul 2007 01:47:59 -0700
Subject: readahead: data structure and routines

Extend struct file_ra_state to support the on-demand readahead logic.  Also
define some helpers for it.

Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Steven Pratt <slpratt@austin.ibm.com>
Cc: Ram Pai <linuxram@us.ibm.com>
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/readahead.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'mm')

diff --git a/mm/readahead.c b/mm/readahead.c
index 7f9bf588c93..072ce8f8357 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -592,3 +592,22 @@ unsigned long max_sane_readahead(unsigned long nr)
 	return min(nr, (node_page_state(numa_node_id(), NR_INACTIVE)
 		+ node_page_state(numa_node_id(), NR_FREE_PAGES)) / 2);
 }
+
+/*
+ * Submit IO for the read-ahead request in file_ra_state.
+ */
+unsigned long ra_submit(struct file_ra_state *ra,
+		       struct address_space *mapping, struct file *filp)
+{
+	unsigned long ra_size;
+	unsigned long la_size;
+	int actual;
+
+	ra_size = ra_readahead_size(ra);
+	la_size = ra_lookahead_size(ra);
+	actual = __do_page_cache_readahead(mapping, filp,
+					ra->ra_index, ra_size, la_size);
+
+	return actual;
+}
+EXPORT_SYMBOL_GPL(ra_submit);
-- 
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