fs: move pipe sysctls to is own file

kernel/sysctl.c is a kitchen sink where everyone leaves their dirty
dishes, this makes it very difficult to maintain.

To help with this maintenance let's start by moving sysctls to places
where they actually belong.  The proc sysctl maintainers do not want to
know what sysctl knobs you wish to add for your own piece of code, we
just care about the core logic.

So move the pipe sysctls to its own file.

Link: https://lkml.kernel.org/r/20211129205548.605569-10-mcgrof@kernel.org
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Antti Palosaari <crope@iki.fi>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Lukas Middendorf <kernel@tuxforce.de>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Xiaoming Ni <nixiaoming@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 61 insertions, 3 deletions

diff --git a/fs/pipe.c b/fs/pipe.c
index 6d4342bad9f1..cc28623a67b6 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -25,6 +25,7 @@
 #include <linux/fcntl.h>
 #include <linux/memcontrol.h>
 #include <linux/watch_queue.h>
+#include <linux/sysctl.h>
 
 #include <linux/uaccess.h>
 #include <asm/ioctls.h>
@@ -50,13 +51,13 @@
  * The max size that a non-root user is allowed to grow the pipe. Can
  * be set by root in /proc/sys/fs/pipe-max-size
  */
-unsigned int pipe_max_size = 1048576;
+static unsigned int pipe_max_size = 1048576;
 
 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
  * matches default values.
  */
-unsigned long pipe_user_pages_hard;
-unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
+static unsigned long pipe_user_pages_hard;
+static unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
 
 /*
  * We use head and tail indices that aren't masked off, except at the point of
@@ -1428,6 +1429,60 @@ static struct file_system_type pipe_fs_type = {
 	.kill_sb	= kill_anon_super,
 };
 
+#ifdef CONFIG_SYSCTL
+static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
+					unsigned int *valp,
+					int write, void *data)
+{
+	if (write) {
+		unsigned int val;
+
+		val = round_pipe_size(*lvalp);
+		if (val == 0)
+			return -EINVAL;
+
+		*valp = val;
+	} else {
+		unsigned int val = *valp;
+		*lvalp = (unsigned long) val;
+	}
+
+	return 0;
+}
+
+static int proc_dopipe_max_size(struct ctl_table *table, int write,
+				void *buffer, size_t *lenp, loff_t *ppos)
+{
+	return do_proc_douintvec(table, write, buffer, lenp, ppos,
+				 do_proc_dopipe_max_size_conv, NULL);
+}
+
+static struct ctl_table fs_pipe_sysctls[] = {
+	{
+		.procname	= "pipe-max-size",
+		.data		= &pipe_max_size,
+		.maxlen		= sizeof(pipe_max_size),
+		.mode		= 0644,
+		.proc_handler	= proc_dopipe_max_size,
+	},
+	{
+		.procname	= "pipe-user-pages-hard",
+		.data		= &pipe_user_pages_hard,
+		.maxlen		= sizeof(pipe_user_pages_hard),
+		.mode		= 0644,
+		.proc_handler	= proc_doulongvec_minmax,
+	},
+	{
+		.procname	= "pipe-user-pages-soft",
+		.data		= &pipe_user_pages_soft,
+		.maxlen		= sizeof(pipe_user_pages_soft),
+		.mode		= 0644,
+		.proc_handler	= proc_doulongvec_minmax,
+	},
+	{ }
+};
+#endif
+
 static int __init init_pipe_fs(void)
 {
 	int err = register_filesystem(&pipe_fs_type);
@@ -1439,6 +1494,9 @@ static int __init init_pipe_fs(void)
 			unregister_filesystem(&pipe_fs_type);
 		}
 	}
+#ifdef CONFIG_SYSCTL
+	register_sysctl_init("fs", fs_pipe_sysctls);
+#endif
 	return err;
 }