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/proc/swaps: support polling

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System management wants to subscribe to changes in swap configuration.
Make /proc/swaps pollable like /proc/mounts.

[akpm@linux-foundation.org: document proc_poll_event]
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Acked-by: Greg KH <greg@kroah.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kay Sievers 2010-10-26 14:22:06 -07:00 committed by Linus Torvalds
parent e1ca7788de
commit 66d7dd518a
1 changed files with 48 additions and 1 deletions
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49
mm/swapfile.c
View File

@ -30,6 +30,7 @@
#include <linux/capability.h>
#include <linux/syscalls.h>
#include <linux/memcontrol.h>
#include <linux/poll.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
@ -58,6 +59,10 @@ static struct swap_info_struct *swap_info[MAX_SWAPFILES];
static DEFINE_MUTEX(swapon_mutex);
static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
/* Activity counter to indicate that a swapon or swapoff has occurred */
static atomic_t proc_poll_event = ATOMIC_INIT(0);
static inline unsigned char swap_count(unsigned char ent)
{
return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
@ -1680,6 +1685,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
}
filp_close(swap_file, NULL);
err = 0;
atomic_inc(&proc_poll_event);
wake_up_interruptible(&proc_poll_wait);
out_dput:
filp_close(victim, NULL);
@ -1688,6 +1695,25 @@ out:
}
#ifdef CONFIG_PROC_FS
struct proc_swaps {
struct seq_file seq;
int event;
};
static unsigned swaps_poll(struct file *file, poll_table *wait)
{
struct proc_swaps *s = file->private_data;
poll_wait(file, &proc_poll_wait, wait);
if (s->event != atomic_read(&proc_poll_event)) {
s->event = atomic_read(&proc_poll_event);
return POLLIN | POLLRDNORM | POLLERR | POLLPRI;
}
return POLLIN | POLLRDNORM;
}
/* iterator */
static void *swap_start(struct seq_file *swap, loff_t *pos)
{
@ -1771,7 +1797,24 @@ static const struct seq_operations swaps_op = {
static int swaps_open(struct inode *inode, struct file *file)
{
return seq_open(file, &swaps_op);
struct proc_swaps *s;
int ret;
s = kmalloc(sizeof(struct proc_swaps), GFP_KERNEL);
if (!s)
return -ENOMEM;
file->private_data = s;
ret = seq_open(file, &swaps_op);
if (ret) {
kfree(s);
return ret;
}
s->seq.private = s;
s->event = atomic_read(&proc_poll_event);
return ret;
}
static const struct file_operations proc_swaps_operations = {
@ -1779,6 +1822,7 @@ static const struct file_operations proc_swaps_operations = {
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
.poll = swaps_poll,
};
static int __init procswaps_init(void)
@ -2084,6 +2128,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
swap_info[prev]->next = type;
spin_unlock(&swap_lock);
mutex_unlock(&swapon_mutex);
atomic_inc(&proc_poll_event);
wake_up_interruptible(&proc_poll_wait);
error = 0;
goto out;
bad_swap: