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Commit 66d7dd51 authored by Kay Sievers's avatar Kay Sievers Committed by Linus Torvalds
Browse files

/proc/swaps: support polling 



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: default avatarKay Sievers <kay.sievers@vrfy.org>
Acked-by: default avatarGreg KH <greg@kroah.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e1ca7788

mm/swapfile.c

+48 −1
Original line number Original line Diff line number Diff line
@@ -30,6 +30,7 @@ 
#include <linux/capability.h>

#include <linux/capability.h>

#include <linux/syscalls.h>

#include <linux/syscalls.h>

#include <linux/memcontrol.h>

#include <linux/memcontrol.h>

#include <linux/poll.h>





#include <asm/pgtable.h>

#include <asm/pgtable.h>

#include <asm/tlbflush.h>

#include <asm/tlbflush.h>
@@ -58,6 +59,10 @@ static struct swap_info_struct *swap_info[MAX_SWAPFILES]; 




static DEFINE_MUTEX(swapon_mutex);

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)

static inline unsigned char swap_count(unsigned char ent)

{

{

	return ent & ~SWAP_HAS_CACHE;	/* may include SWAP_HAS_CONT flag */

	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);

	filp_close(swap_file, NULL);

	err = 0;

	err = 0;

	atomic_inc(&proc_poll_event);

	wake_up_interruptible(&proc_poll_wait);





out_dput:

out_dput:

	filp_close(victim, NULL);

	filp_close(victim, NULL);
@@ -1688,6 +1695,25 @@ out: 
}

}





#ifdef CONFIG_PROC_FS

#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 */

/* iterator */

static void *swap_start(struct seq_file *swap, loff_t *pos)

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)

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 = {

static const struct file_operations proc_swaps_operations = {
@@ -1779,6 +1822,7 @@ static const struct file_operations proc_swaps_operations = { 
	.read		= seq_read,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.llseek		= seq_lseek,

	.release	= seq_release,

	.release	= seq_release,

	.poll		= swaps_poll,

};

};





static int __init procswaps_init(void)

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;

		swap_info[prev]->next = type;

	spin_unlock(&swap_lock);

	spin_unlock(&swap_lock);

	mutex_unlock(&swapon_mutex);

	mutex_unlock(&swapon_mutex);

	atomic_inc(&proc_poll_event);

	wake_up_interruptible(&proc_poll_wait);



	error = 0;

	error = 0;

	goto out;

	goto out;

bad_swap:

bad_swap: