From b492e95be0ae672922f4734acf3f5d35c30be948 Mon Sep 17 00:00:00 2001
From: Jens Axboe <jens.axboe@oracle.com>
Date: Wed, 19 May 2010 21:03:16 +0200
Subject: pipe: set lower and upper limit on max pages in the pipe page array

We need at least two to guarantee proper POSIX behaviour, so
never allow a smaller limit than that.

Also expose a /proc/sys/fs/pipe-max-pages sysctl file that allows
root to define a sane upper limit. Make it default to 16 times the
default size, which is 16 pages.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
 kernel/sysctl.c | 9 +++++++++
 1 file changed, 9 insertions(+)

(limited to 'kernel')

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8686b0f5fc1..c649d1c5fe0 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -52,6 +52,7 @@
 #include <linux/slow-work.h>
 #include <linux/perf_event.h>
 #include <linux/kprobes.h>
+#include <linux/pipe_fs_i.h>
 
 #include <asm/uaccess.h>
 #include <asm/processor.h>
@@ -1423,6 +1424,14 @@ static struct ctl_table fs_table[] = {
 		.child		= binfmt_misc_table,
 	},
 #endif
+	{
+		.procname	= "pipe-max-pages",
+		.data		= &pipe_max_pages,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_minmax,
+		.extra1		= &two,
+	},
 /*
  * NOTE: do not add new entries to this table unless you have read
  * Documentation/sysctl/ctl_unnumbered.txt
-- 
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