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Subject[PATCH] Make sysctl a separate filesystem
Sysctl files/inodes now have their own readdir and lookup
methods, so there is one step left in turning this into a
separate filesystem.

The benefits of this are:

1. this will allow to remove a fancy revalidation rules from
sysctl dentries (will be in a separate patch);
2. the same approach will make /proc/net implementation MUCH
cleaner in respect to net namespaces interaction, i.e.
no racy shadows and no revalidation for proc entries in
this subdir;
3. sysctl inodes are now smaller than the procfs ones.

Note: update your initscripts to mount sysctl filesystem
right after the proc is mounted in order not to lose your
/etc/sysctl.conf configuration (and optionally fstab).

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>

---
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 1c81c8f..47dec4b 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -11,11 +11,6 @@

#include <linux/proc_fs.h>

-#ifdef CONFIG_PROC_SYSCTL
-extern int proc_sys_init(void);
-#else
-static inline void proc_sys_init(void) { }
-#endif
#ifdef CONFIG_NET
extern int proc_net_init(void);
#else
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 614c34b..1b52f43 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1,11 +1,9 @@
/*
* /proc/sys support
*/
-
+#include <linux/magic.h>
#include <linux/sysctl.h>
-#include <linux/proc_fs.h>
#include <linux/security.h>
-#include "internal.h"

static struct dentry_operations proc_sys_dentry_operations;
static const struct file_operations proc_sys_file_operations;
@@ -28,22 +26,26 @@ static void proc_sys_refresh_inode(struct inode *inode, struct ctl_table *table)
}
}

+static inline long inode_depth(struct inode *ino)
+{
+ return (long)ino->i_private;
+}
+
+static inline void set_inode_depth(struct inode *ino, long depth)
+{
+ ino->i_private = (void *)depth;
+}
+
static struct inode *proc_sys_make_inode(struct inode *dir, struct ctl_table *table)
{
struct inode *inode;
- struct proc_inode *dir_ei, *ei;
- int depth;

inode = new_inode(dir->i_sb);
if (!inode)
goto out;

/* A directory is always one deeper than it's parent */
- dir_ei = PROC_I(dir);
- depth = dir_ei->fd + 1;
-
- ei = PROC_I(inode);
- ei->fd = depth;
+ set_inode_depth(inode, inode_depth(dir) + 1);
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_op = &proc_sys_inode_operations;
inode->i_fop = &proc_sys_file_operations;
@@ -56,10 +58,7 @@ out:
static struct dentry *proc_sys_ancestor(struct dentry *dentry, int depth)
{
for (;;) {
- struct proc_inode *ei;
-
- ei = PROC_I(dentry->d_inode);
- if (ei->fd == depth)
+ if (inode_depth(dentry->d_inode) == depth)
break; /* found */

dentry = dentry->d_parent;
@@ -93,12 +92,9 @@ static struct ctl_table *proc_sys_lookup_table(struct dentry *dentry,
struct ctl_table *table)
{
struct dentry *ancestor;
- struct proc_inode *ei;
int depth, i;

- ei = PROC_I(dentry->d_inode);
- depth = ei->fd;
-
+ depth = inode_depth(dentry->d_inode);
if (depth == 0)
return table;

@@ -385,7 +381,7 @@ static int proc_sys_permission(struct inode *inode, int mask, struct nameidata *
int error;

head = NULL;
- depth = PROC_I(inode)->fd;
+ depth = inode_depth(inode);

/* First check the cached permissions, in case we don't have
* enough information to lookup the sysctl table entry.
@@ -466,13 +462,56 @@ static struct dentry_operations proc_sys_dentry_operations = {
.d_revalidate = proc_sys_revalidate,
};

-static struct proc_dir_entry *proc_sys_root;
+static const struct super_operations sysctl_ops = {
+ .statfs = simple_statfs,
+ .drop_inode = generic_delete_inode,
+};

-int proc_sys_init(void)
+static int sysctl_fill_super(struct super_block *sb, void *data, int flags)
{
- proc_sys_root = proc_mkdir("sys", NULL);
- proc_sys_root->proc_iops = &proc_sys_inode_operations;
- proc_sys_root->proc_fops = &proc_sys_file_operations;
- proc_sys_root->nlink = 0;
+ struct inode *ino;
+
+ sb->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC | MS_NODEV;
+ sb->s_blocksize = 1024;
+ sb->s_blocksize_bits = 10;
+ sb->s_magic = PROC_SUPER_MAGIC;
+ sb->s_op = &sysctl_ops;
+ sb->s_time_gran = 1;
+
+ ino = new_inode(sb);
+ if (ino == NULL)
+ return -ENOMEM;
+
+ ino->i_op = &proc_sys_inode_operations;
+ ino->i_fop = &proc_sys_file_operations;
+ set_inode_depth(ino, 0);
+ ino->i_uid = 0;
+ ino->i_gid = 0;
+ ino->i_mode = 0555 | S_IFDIR;
+
+ sb->s_root = d_alloc_root(ino);
+ if (sb->s_root == NULL) {
+ iput(ino);
+ return -ENOMEM;
+ }
+
return 0;
}
+
+static int sysctl_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev_name, void *data, struct vfsmount *mnt)
+{
+ return get_sb_single(fs_type, flags, data, sysctl_fill_super, mnt);
+}
+
+static struct file_system_type sysctl_fs = {
+ .name = "sysctl",
+ .get_sb = sysctl_get_sb,
+ .kill_sb = kill_anon_super,
+};
+
+static int __init proc_sys_init(void)
+{
+ return register_filesystem(&sysctl_fs);
+}
+module_init(proc_sys_init);
diff --git a/fs/proc/root.c b/fs/proc/root.c
index ef0fb57..9035938 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -129,6 +129,7 @@ void __init proc_root_init(void)
proc_root_fs = proc_mkdir("fs", NULL);
proc_root_driver = proc_mkdir("driver", NULL);
proc_mkdir("fs/nfsd", NULL); /* somewhere for the nfsd filesystem to be mounted */
+ proc_mkdir("sys", NULL);
#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
/* just give it a mountpoint */
proc_mkdir("openprom", NULL);
@@ -138,7 +139,6 @@ void __init proc_root_init(void)
proc_device_tree_init();
#endif
proc_bus = proc_mkdir("bus", NULL);
- proc_sys_init();
}

static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat


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