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sysctl: add support for poll()

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Adding support for poll() in sysctl fs allows userspace to receive
notifications of changes in sysctl entries.  This adds a infrastructure to
allow files in sysctl fs to be pollable and implements it for hostname and
domainname.

[akpm@linux-foundation.org: s/declare/define/ for definitions]
Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: Greg KH <gregkh@suse.de>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Lucas De Marchi 2011-11-02 13:39:22 -07:00 committed by Linus Torvalds
parent 088024b1de
commit f1ecf06854
5 changed files with 108 additions and 0 deletions
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45
fs/proc/proc_sysctl.c
View File

@ -3,6 +3,7 @@
*/
#include <linux/init.h>
#include <linux/sysctl.h>
#include <linux/poll.h>
#include <linux/proc_fs.h>
#include <linux/security.h>
#include <linux/namei.h>
@ -14,6 +15,15 @@ static const struct inode_operations proc_sys_inode_operations;
static const struct file_operations proc_sys_dir_file_operations;
static const struct inode_operations proc_sys_dir_operations;
void proc_sys_poll_notify(struct ctl_table_poll *poll)
{
if (!poll)
return;
atomic_inc(&poll->event);
wake_up_interruptible(&poll->wait);
}
static struct inode *proc_sys_make_inode(struct super_block *sb,
struct ctl_table_header *head, struct ctl_table *table)
{
@ -176,6 +186,39 @@ static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
}
static int proc_sys_open(struct inode *inode, struct file *filp)
{
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
if (table->poll)
filp->private_data = proc_sys_poll_event(table->poll);
return 0;
}
static unsigned int proc_sys_poll(struct file *filp, poll_table *wait)
{
struct inode *inode = filp->f_path.dentry->d_inode;
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
unsigned long event = (unsigned long)filp->private_data;
unsigned int ret = DEFAULT_POLLMASK;
if (!table->proc_handler)
goto out;
if (!table->poll)
goto out;
poll_wait(filp, &table->poll->wait, wait);
if (event != atomic_read(&table->poll->event)) {
filp->private_data = proc_sys_poll_event(table->poll);
ret = POLLIN | POLLRDNORM | POLLERR | POLLPRI;
}
out:
return ret;
}
static int proc_sys_fill_cache(struct file *filp, void *dirent,
filldir_t filldir,
@ -364,6 +407,8 @@ static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct
}
static const struct file_operations proc_sys_file_operations = {
.open = proc_sys_open,
.poll = proc_sys_poll,
.read = proc_sys_read,
.write = proc_sys_write,
.llseek = default_llseek,

22
include/linux/sysctl.h
View File

@ -931,6 +931,7 @@ enum
#ifdef __KERNEL__
#include <linux/list.h>
#include <linux/rcupdate.h>
#include <linux/wait.h>
/* For the /proc/sys support */
struct ctl_table;
@ -1011,6 +1012,26 @@ extern int proc_do_large_bitmap(struct ctl_table *, int,
* cover common cases.
*/
/* Support for userspace poll() to watch for changes */
struct ctl_table_poll {
atomic_t event;
wait_queue_head_t wait;
};
static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
{
return (void *)(unsigned long)atomic_read(&poll->event);
}
void proc_sys_poll_notify(struct ctl_table_poll *poll);
#define __CTL_TABLE_POLL_INITIALIZER(name) { \
.event = ATOMIC_INIT(0), \
.wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.wait) }
#define DEFINE_CTL_TABLE_POLL(name) \
struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
/* A sysctl table is an array of struct ctl_table: */
struct ctl_table
{
@ -1021,6 +1042,7 @@ struct ctl_table
struct ctl_table *child;
struct ctl_table *parent; /* Automatically set */
proc_handler *proc_handler; /* Callback for text formatting */
struct ctl_table_poll *poll;
void *extra1;
void *extra2;
};

16
include/linux/utsname.h
View File

@ -37,6 +37,14 @@ struct new_utsname {
#include <linux/nsproxy.h>
#include <linux/err.h>
enum uts_proc {
UTS_PROC_OSTYPE,
UTS_PROC_OSRELEASE,
UTS_PROC_VERSION,
UTS_PROC_HOSTNAME,
UTS_PROC_DOMAINNAME,
};
struct user_namespace;
extern struct user_namespace init_user_ns;
@ -80,6 +88,14 @@ static inline struct uts_namespace *copy_utsname(unsigned long flags,
}
#endif
#ifdef CONFIG_PROC_SYSCTL
extern void uts_proc_notify(enum uts_proc proc);
#else
static inline void uts_proc_notify(enum uts_proc proc)
{
}
#endif
static inline struct new_utsname *utsname(void)
{
return &current->nsproxy->uts_ns->name;

2
kernel/sys.c
View File

@ -1286,6 +1286,7 @@ SYSCALL_DEFINE2(sethostname, char __user *, name, int, len)
memset(u->nodename + len, 0, sizeof(u->nodename) - len);
errno = 0;
}
uts_proc_notify(UTS_PROC_HOSTNAME);
up_write(&uts_sem);
return errno;
}
@ -1336,6 +1337,7 @@ SYSCALL_DEFINE2(setdomainname, char __user *, name, int, len)
memset(u->domainname + len, 0, sizeof(u->domainname) - len);
errno = 0;
}
uts_proc_notify(UTS_PROC_DOMAINNAME);
up_write(&uts_sem);
return errno;
}

23
kernel/utsname_sysctl.c
View File

@ -13,6 +13,7 @@
#include <linux/uts.h>
#include <linux/utsname.h>
#include <linux/sysctl.h>
#include <linux/wait.h>
static void *get_uts(ctl_table *table, int write)
{
@ -51,12 +52,19 @@ static int proc_do_uts_string(ctl_table *table, int write,
uts_table.data = get_uts(table, write);
r = proc_dostring(&uts_table,write,buffer,lenp, ppos);
put_uts(table, write, uts_table.data);
if (write)
proc_sys_poll_notify(table->poll);
return r;
}
#else
#define proc_do_uts_string NULL
#endif
static DEFINE_CTL_TABLE_POLL(hostname_poll);
static DEFINE_CTL_TABLE_POLL(domainname_poll);
static struct ctl_table uts_kern_table[] = {
{
.procname = "ostype",
@ -85,6 +93,7 @@ static struct ctl_table uts_kern_table[] = {
.maxlen = sizeof(init_uts_ns.name.nodename),
.mode = 0644,
.proc_handler = proc_do_uts_string,
.poll = &hostname_poll,
},
{
.procname = "domainname",
@ -92,6 +101,7 @@ static struct ctl_table uts_kern_table[] = {
.maxlen = sizeof(init_uts_ns.name.domainname),
.mode = 0644,
.proc_handler = proc_do_uts_string,
.poll = &domainname_poll,
},
{}
};
@ -105,6 +115,19 @@ static struct ctl_table uts_root_table[] = {
{}
};
#ifdef CONFIG_PROC_SYSCTL
/*
* Notify userspace about a change in a certain entry of uts_kern_table,
* identified by the parameter proc.
*/
void uts_proc_notify(enum uts_proc proc)
{
struct ctl_table *table = &uts_kern_table[proc];
proc_sys_poll_notify(table->poll);
}
#endif
static int __init utsname_sysctl_init(void)
{
register_sysctl_table(uts_root_table);