sysctl: add support for poll()
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>
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index dacd840..df59480 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -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 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 @@
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 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,