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[PATCH] sysctl: reimplement the sysctl proc support 

With this change the sysctl inodes can be cached and nothing needs to be done
when removing a sysctl table.

For a cost of 2K code we will save about 4K of static tables (when we remove
de from ctl_table) and 70K in proc_dir_entries that we will not allocate, or
about half that on a 32bit arch.

The speed feels about the same, even though we can now cache the sysctl
dentries :(

We get the core advantage that we don't need to have a 1 to 1 mapping between
ctl table entries and proc files.  Making it possible to have /proc/sys vary
depending on the namespace you are in.  The currently merged namespaces don't
have an issue here but the network namespace under /proc/sys/net needs to have
different directories depending on which network adapters are visible.  By
simply being a cache different directories being visible depending on who you
are is trivial to implement.

[akpm@osdl.org: fix uninitialised var]
[akpm@osdl.org: fix ARM build]
[bunk@stusta.de: make things static]
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric W. Biederman 2007-02-14 00:34:12 -08:00 committed by Linus Torvalds
parent 1ff007eb8e
commit 77b14db502
10 changed files with 486 additions and 199 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/proc/Makefile
View File

@ -8,7 +8,7 @@ proc-y := nommu.o task_nommu.o
proc-$(CONFIG_MMU) := mmu.o task_mmu.o
proc-y += inode.o root.o base.o generic.o array.o \
proc_tty.o proc_misc.o
proc_tty.o proc_misc.o proc_sysctl.o
proc-$(CONFIG_PROC_KCORE) += kcore.o
proc-$(CONFIG_PROC_VMCORE) += vmcore.o

2
fs/proc/generic.c
View File

@ -32,7 +32,7 @@ static loff_t proc_file_lseek(struct file *, loff_t, int);
DEFINE_SPINLOCK(proc_subdir_lock);
int proc_match(int len, const char *name, struct proc_dir_entry *de)
static int proc_match(int len, const char *name, struct proc_dir_entry *de)
{
if (de->namelen != len)
return 0;

1
fs/proc/inode.c
View File

@ -161,6 +161,7 @@ struct inode *proc_get_inode(struct super_block *sb, unsigned int ino,
if (!inode)
goto out_ino;
PROC_I(inode)->fd = 0;
PROC_I(inode)->pde = de;
if (de) {
if (de->mode) {

2
fs/proc/internal.h
View File

@ -11,6 +11,8 @@
#include <linux/proc_fs.h>
extern int proc_sys_init(void);
struct vmalloc_info {
unsigned long used;
unsigned long largest_chunk;

478
fs/proc/proc_sysctl.c Normal file
View File

@ -0,0 +1,478 @@
/*
* /proc/sys support
*/
#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;
static struct inode_operations proc_sys_inode_operations;
static void proc_sys_refresh_inode(struct inode *inode, struct ctl_table *table)
{
/* Refresh the cached information bits in the inode */
if (table) {
inode->i_uid = 0;
inode->i_gid = 0;
inode->i_mode = table->mode;
if (table->proc_handler) {
inode->i_mode |= S_IFREG;
inode->i_nlink = 1;
} else {
inode->i_mode |= S_IFDIR;
inode->i_nlink = 0; /* It is too hard to figure out */
}
}
}
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;
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;
proc_sys_refresh_inode(inode, table);
out:
return inode;
}
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)
break; /* found */
dentry = dentry->d_parent;
}
return dentry;
}
static struct ctl_table *proc_sys_lookup_table_one(struct ctl_table *table,
struct qstr *name)
{
int len;
for ( ; table->ctl_name || table->procname; table++) {
if (!table->procname)
continue;
len = strlen(table->procname);
if (len != name->len)
continue;
if (memcmp(table->procname, name->name, len) != 0)
continue;
/* I have a match */
return table;
}
return NULL;
}
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;
if (depth == 0)
return table;
for (i = 1; table && (i <= depth); i++) {
ancestor = proc_sys_ancestor(dentry, i);
table = proc_sys_lookup_table_one(table, &ancestor->d_name);
if (table)
table = table->child;
}
return table;
}
static struct ctl_table *proc_sys_lookup_entry(struct dentry *dparent,
struct qstr *name,
struct ctl_table *table)
{
table = proc_sys_lookup_table(dparent, table);
if (table)
table = proc_sys_lookup_table_one(table, name);
return table;
}
static struct ctl_table *do_proc_sys_lookup(struct dentry *parent,
struct qstr *name,
struct ctl_table_header **ptr)
{
struct ctl_table_header *head;
struct ctl_table *table = NULL;
for (head = sysctl_head_next(NULL); head;
head = sysctl_head_next(head)) {
table = proc_sys_lookup_entry(parent, name, head->ctl_table);
if (table)
break;
}
*ptr = head;
return table;
}
static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
struct nameidata *nd)
{
struct ctl_table_header *head;
struct inode *inode;
struct dentry *err;
struct ctl_table *table;
err = ERR_PTR(-ENOENT);
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
if (!table)
goto out;
err = ERR_PTR(-ENOMEM);
inode = proc_sys_make_inode(dir, table);
if (!inode)
goto out;
err = NULL;
dentry->d_op = &proc_sys_dentry_operations;
d_add(dentry, inode);
out:
sysctl_head_finish(head);
return err;
}
static ssize_t proc_sys_read(struct file *filp, char __user *buf,
size_t count, loff_t *ppos)
{
struct dentry *dentry = filp->f_dentry;
struct ctl_table_header *head;
struct ctl_table *table;
ssize_t error, res;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
/* Has the sysctl entry disappeared on us? */
error = -ENOENT;
if (!table)
goto out;
/* Has the sysctl entry been replaced by a directory? */
error = -EISDIR;
if (!table->proc_handler)
goto out;
/*
* At this point we know that the sysctl was not unregistered
* and won't be until we finish.
*/
error = -EPERM;
if (sysctl_perm(table, MAY_READ))
goto out;
/* careful: calling conventions are nasty here */
res = count;
error = table->proc_handler(table, 0, filp, buf, &res, ppos);
if (!error)
error = res;
out:
sysctl_head_finish(head);
return error;
}
static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
size_t count, loff_t *ppos)
{
struct dentry *dentry = filp->f_dentry;
struct ctl_table_header *head;
struct ctl_table *table;
ssize_t error, res;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
/* Has the sysctl entry disappeared on us? */
error = -ENOENT;
if (!table)
goto out;
/* Has the sysctl entry been replaced by a directory? */
error = -EISDIR;
if (!table->proc_handler)
goto out;
/*
* At this point we know that the sysctl was not unregistered
* and won't be until we finish.
*/
error = -EPERM;
if (sysctl_perm(table, MAY_WRITE))
goto out;
/* careful: calling conventions are nasty here */
res = count;
error = table->proc_handler(table, 1, filp, (char __user *)buf,
&res, ppos);
if (!error)
error = res;
out:
sysctl_head_finish(head);
return error;
}
static int proc_sys_fill_cache(struct file *filp, void *dirent,
filldir_t filldir, struct ctl_table *table)
{
struct ctl_table_header *head;
struct ctl_table *child_table = NULL;
struct dentry *child, *dir = filp->f_path.dentry;
struct inode *inode;
struct qstr qname;
ino_t ino = 0;
unsigned type = DT_UNKNOWN;
int ret;
qname.name = table->procname;
qname.len = strlen(table->procname);
qname.hash = full_name_hash(qname.name, qname.len);
/* Suppress duplicates.
* Only fill a directory entry if it is the value that
* an ordinary lookup of that name returns. Hide all
* others.
*
* If we ever cache this translation in the dcache
* I should do a dcache lookup first. But for now
* it is just simpler not to.
*/
ret = 0;
child_table = do_proc_sys_lookup(dir, &qname, &head);
sysctl_head_finish(head);
if (child_table != table)
return 0;
child = d_lookup(dir, &qname);
if (!child) {
struct dentry *new;
new = d_alloc(dir, &qname);
if (new) {
inode = proc_sys_make_inode(dir->d_inode, table);
if (!inode)
child = ERR_PTR(-ENOMEM);
else {
new->d_op = &proc_sys_dentry_operations;
d_add(new, inode);
}
if (child)
dput(new);
else
child = new;
}
}
if (!child || IS_ERR(child) || !child->d_inode)
goto end_instantiate;
inode = child->d_inode;
if (inode) {
ino = inode->i_ino;
type = inode->i_mode >> 12;
}
dput(child);
end_instantiate:
if (!ino)
ino= find_inode_number(dir, &qname);
if (!ino)
ino = 1;
return filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
}
static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
struct dentry *dentry = filp->f_dentry;
struct inode *inode = dentry->d_inode;
struct ctl_table_header *head = NULL;
struct ctl_table *table;
unsigned long pos;
int ret;
ret = -ENOTDIR;
if (!S_ISDIR(inode->i_mode))
goto out;
ret = 0;
/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
if (filp->f_pos == 0) {
if (filldir(dirent, ".", 1, filp->f_pos,
inode->i_ino, DT_DIR) < 0)
goto out;
filp->f_pos++;
}
if (filp->f_pos == 1) {
if (filldir(dirent, "..", 2, filp->f_pos,
parent_ino(dentry), DT_DIR) < 0)
goto out;
filp->f_pos++;
}
pos = 2;
/* - Find each instance of the directory
* - Read all entries in each instance
* - Before returning an entry to user space lookup the entry
* by name and if I find a different entry don't return
* this one because it means it is a buried dup.
* For sysctl this should only happen for directory entries.
*/
for (head = sysctl_head_next(NULL); head; head = sysctl_head_next(head)) {
table = proc_sys_lookup_table(dentry, head->ctl_table);
if (!table)
continue;
for (; table->ctl_name || table->procname; table++, pos++) {
/* Can't do anything without a proc name */
if (!table->procname)
continue;
if (pos < filp->f_pos)
continue;
if (proc_sys_fill_cache(filp, dirent, filldir, table) < 0)
goto out;
filp->f_pos = pos + 1;
}
}
ret = 1;
out:
sysctl_head_finish(head);
return ret;
}
static int proc_sys_permission(struct inode *inode, int mask, struct nameidata *nd)
{
/*
* sysctl entries that are not writeable,
* are _NOT_ writeable, capabilities or not.
*/
struct ctl_table_header *head;
struct ctl_table *table;
struct dentry *dentry;
int mode;
int depth;
int error;
head = NULL;
depth = PROC_I(inode)->fd;
/* First check the cached permissions, in case we don't have
* enough information to lookup the sysctl table entry.
*/
error = -EACCES;
mode = inode->i_mode;
if (current->euid == 0)
mode >>= 6;
else if (in_group_p(0))
mode >>= 3;
if ((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask)
error = 0;
/* If we can't get a sysctl table entry the permission
* checks on the cached mode will have to be enough.
*/
if (!nd || !depth)
goto out;
dentry = nd->dentry;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
/* If the entry does not exist deny permission */
error = -EACCES;
if (!table)
goto out;
/* Use the permissions on the sysctl table entry */
error = sysctl_perm(table, mask);
out:
sysctl_head_finish(head);
return error;
}
static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = dentry->d_inode;
int error;
if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
return -EPERM;
error = inode_change_ok(inode, attr);
if (!error) {
error = security_inode_setattr(dentry, attr);
if (!error)
error = inode_setattr(inode, attr);
}
return error;
}
/* I'm lazy and don't distinguish between files and directories,
* until access time.
*/
static const struct file_operations proc_sys_file_operations = {
.read = proc_sys_read,
.write = proc_sys_write,
.readdir = proc_sys_readdir,
};
static struct inode_operations proc_sys_inode_operations = {
.lookup = proc_sys_lookup,
.permission = proc_sys_permission,
.setattr = proc_sys_setattr,
};
static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
{
struct ctl_table_header *head;
struct ctl_table *table;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
proc_sys_refresh_inode(dentry->d_inode, table);
sysctl_head_finish(head);
return !!table;
}
static struct dentry_operations proc_sys_dentry_operations = {
.d_revalidate = proc_sys_revalidate,
};
static struct proc_dir_entry *proc_sys_root;
int proc_sys_init(void)
{
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;
return 0;
}

10
fs/proc/root.c
View File

@ -23,10 +23,6 @@
struct proc_dir_entry *proc_net, *proc_net_stat, *proc_bus, *proc_root_fs, *proc_root_driver;
#ifdef CONFIG_SYSCTL
struct proc_dir_entry *proc_sys_root;
#endif
static int proc_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
@ -70,9 +66,6 @@ void __init proc_root_init(void)
#ifdef CONFIG_SYSVIPC
proc_mkdir("sysvipc", NULL);
#endif
#ifdef CONFIG_SYSCTL
proc_sys_root = proc_mkdir("sys", NULL);
#endif
proc_root_fs = proc_mkdir("fs", NULL);
proc_root_driver = proc_mkdir("driver", NULL);
@ -86,6 +79,9 @@ void __init proc_root_init(void)
proc_device_tree_init();
#endif
proc_bus = proc_mkdir("bus", NULL);
#ifdef CONFIG_SYSCTL
proc_sys_init();
#endif
}
static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat

2
include/linux/proc_fs.h
View File

@ -113,8 +113,6 @@ extern struct vfsmount *proc_mnt;
extern int proc_fill_super(struct super_block *,void *,int);
extern struct inode *proc_get_inode(struct super_block *, unsigned int, struct proc_dir_entry *);
extern int proc_match(int, const char *,struct proc_dir_entry *);
/*
* These are generic /proc routines that use the internal
* "struct proc_dir_entry" tree to traverse the filesystem.

2
include/linux/sysctl.h
View File

@ -930,8 +930,6 @@ extern struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev);
extern void sysctl_head_finish(struct ctl_table_header *prev);
extern int sysctl_perm(struct ctl_table *table, int op);
extern void sysctl_init(void);
typedef struct ctl_table ctl_table;
typedef int ctl_handler (ctl_table *table, int __user *name, int nlen,

4
init/main.c
View File

@ -86,7 +86,6 @@ extern void init_IRQ(void);
extern void fork_init(unsigned long);
extern void mca_init(void);
extern void sbus_init(void);
extern void sysctl_init(void);
extern void signals_init(void);
extern void pidhash_init(void);
extern void pidmap_init(void);
@ -702,9 +701,6 @@ static void __init do_basic_setup(void)
usermodehelper_init();
driver_init();
#ifdef CONFIG_SYSCTL
sysctl_init();
#endif
#ifdef CONFIG_PROC_FS
init_irq_proc();
#endif

182
kernel/sysctl.c
View File

@ -159,26 +159,6 @@ int sysctl_legacy_va_layout;
#endif
/* /proc declarations: */
#ifdef CONFIG_PROC_SYSCTL
static ssize_t proc_readsys(struct file *, char __user *, size_t, loff_t *);
static ssize_t proc_writesys(struct file *, const char __user *, size_t, loff_t *);
static int proc_opensys(struct inode *, struct file *);
const struct file_operations proc_sys_file_operations = {
.open = proc_opensys,
.read = proc_readsys,
.write = proc_writesys,
};
extern struct proc_dir_entry *proc_sys_root;
static void register_proc_table(ctl_table *, struct proc_dir_entry *, void *);
static void unregister_proc_table(ctl_table *, struct proc_dir_entry *);
#endif
/* The default sysctl tables: */
static ctl_table root_table[] = {
@ -1106,13 +1086,6 @@ struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev)
return NULL;
}
void __init sysctl_init(void)
{
#ifdef CONFIG_PROC_SYSCTL
register_proc_table(root_table, proc_sys_root, &root_table_header);
#endif
}
#ifdef CONFIG_SYSCTL_SYSCALL
int do_sysctl(int __user *name, int nlen, void __user *oldval, size_t __user *oldlenp,
void __user *newval, size_t newlen)
@ -1348,9 +1321,6 @@ struct ctl_table_header *register_sysctl_table(ctl_table * table)
spin_lock(&sysctl_lock);
list_add_tail(&tmp->ctl_entry, &root_table_header.ctl_entry);
spin_unlock(&sysctl_lock);
#ifdef CONFIG_PROC_SYSCTL
register_proc_table(table, proc_sys_root, tmp);
#endif
return tmp;
}
@ -1366,9 +1336,6 @@ void unregister_sysctl_table(struct ctl_table_header * header)
might_sleep();
spin_lock(&sysctl_lock);
start_unregistering(header);
#ifdef CONFIG_PROC_SYSCTL
unregister_proc_table(header->ctl_table, proc_sys_root);
#endif
spin_unlock(&sysctl_lock);
kfree(header);
}
@ -1392,155 +1359,6 @@ void unregister_sysctl_table(struct ctl_table_header * table)
#ifdef CONFIG_PROC_SYSCTL
/* Scan the sysctl entries in table and add them all into /proc */
static void register_proc_table(ctl_table * table, struct proc_dir_entry *root, void *set)
{
struct proc_dir_entry *de;
int len;
mode_t mode;
for (; table->ctl_name || table->procname; table++) {
/* Can't do anything without a proc name. */
if (!table->procname)
continue;
/* Maybe we can't do anything with it... */
if (!table->proc_handler && !table->child) {
printk(KERN_WARNING "SYSCTL: Can't register %s\n",
table->procname);
continue;
}
len = strlen(table->procname);
mode = table->mode;
de = NULL;
if (table->proc_handler)
mode |= S_IFREG;
else {
mode |= S_IFDIR;
for (de = root->subdir; de; de = de->next) {
if (proc_match(len, table->procname, de))
break;
}
/* If the subdir exists already, de is non-NULL */
}
if (!de) {
de = create_proc_entry(table->procname, mode, root);
if (!de)
continue;
de->set = set;
de->data = (void *) table;
if (table->proc_handler)
de->proc_fops = &proc_sys_file_operations;
}
table->de = de;
if (de->mode & S_IFDIR)
register_proc_table(table->child, de, set);
}
}
/*
* Unregister a /proc sysctl table and any subdirectories.
*/
static void unregister_proc_table(ctl_table * table, struct proc_dir_entry *root)
{
struct proc_dir_entry *de;
for (; table->ctl_name || table->procname; table++) {
if (!(de = table->de))
continue;
if (de->mode & S_IFDIR) {
if (!table->child) {
printk (KERN_ALERT "Help - malformed sysctl tree on free\n");
continue;
}
unregister_proc_table(table->child, de);
/* Don't unregister directories which still have entries.. */
if (de->subdir)
continue;
}
/*
* In any case, mark the entry as goner; we'll keep it
* around if it's busy, but we'll know to do nothing with
* its fields. We are under sysctl_lock here.
*/
de->data = NULL;
/* Don't unregister proc entries that are still being used.. */
if (atomic_read(&de->count))
continue;
table->de = NULL;
remove_proc_entry(table->procname, root);
}
}
static ssize_t do_rw_proc(int write, struct file * file, char __user * buf,
size_t count, loff_t *ppos)
{
int op;
struct proc_dir_entry *de = PDE(file->f_path.dentry->d_inode);
struct ctl_table *table;
size_t res;
ssize_t error = -ENOTDIR;
spin_lock(&sysctl_lock);
if (de && de->data && use_table(de->set)) {
/*
* at that point we know that sysctl was not unregistered
* and won't be until we finish
*/
spin_unlock(&sysctl_lock);
table = (struct ctl_table *) de->data;
if (!table || !table->proc_handler)
goto out;
error = -EPERM;
op = (write ? 002 : 004);
if (sysctl_perm(table, op))
goto out;
/* careful: calling conventions are nasty here */
res = count;
error = (*table->proc_handler)(table, write, file,
buf, &res, ppos);
if (!error)
error = res;
out:
spin_lock(&sysctl_lock);
unuse_table(de->set);
}
spin_unlock(&sysctl_lock);
return error;
}
static int proc_opensys(struct inode *inode, struct file *file)
{
if (file->f_mode & FMODE_WRITE) {
/*
* sysctl entries that are not writable,
* are _NOT_ writable, capabilities or not.
*/
if (!(inode->i_mode & S_IWUSR))
return -EPERM;
}
return 0;
}
static ssize_t proc_readsys(struct file * file, char __user * buf,
size_t count, loff_t *ppos)
{
return do_rw_proc(0, file, buf, count, ppos);
}
static ssize_t proc_writesys(struct file * file, const char __user * buf,
size_t count, loff_t *ppos)
{
return do_rw_proc(1, file, (char __user *) buf, count, ppos);
}
static int _proc_do_string(void* data, int maxlen, int write,
struct file *filp, void __user *buffer,
size_t *lenp, loff_t *ppos)