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SubjectRe: [PATCH] support polling of /proc/swaps
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On Tue, 2010-10-19 at 11:19 +0200, Kay Sievers wrote:
> From: Kay Sievers <kay.sievers@vrfy.org>
> Subject: support polling of /proc/swaps
>
> System management wants to subscribe to changes in swap
> configuration. Make /proc/swaps pollable like /proc/mounts.

And yet you didn't cc any of the mm/ folks on this patch...

> Signed-Off-By: Kay Sievers <kay.sievers@vrfy.org>
> ---
> mm/swapfile.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 47 insertions(+), 1 deletion(-)
>
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -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 +59,9 @@ static struct swap_info_struct *swap_inf
>
> static DEFINE_MUTEX(swapon_mutex);
>
> +static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
> +static int proc_poll_event;
> +
> static inline unsigned char swap_count(unsigned char ent)
> {
> return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */
> @@ -1680,6 +1684,8 @@ SYSCALL_DEFINE1(swapoff, const char __us
> }
> filp_close(swap_file, NULL);
> err = 0;
> + proc_poll_event++;
> + wake_up_interruptible(&proc_poll_wait);
>
> out_dput:
> filp_close(victim, NULL);
> @@ -1688,6 +1694,25 @@ 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 != proc_poll_event) {
> + s->event = 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 +1796,24 @@ static const struct seq_operations swaps
>
> 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->seq;
> +
> + ret = seq_open(file, &swaps_op);
> + if (ret) {
> + kfree(s);
> + return ret;
> + }
> +
> + s->seq.private = s;
> + s->event = proc_poll_event;
> + return ret;
> }
>
> static const struct file_operations proc_swaps_operations = {
> @@ -1779,6 +1821,7 @@ static const struct file_operations proc
> .read = seq_read,
> .llseek = seq_lseek,
> .release = seq_release,
> + .poll = swaps_poll,
> };
>
> static int __init procswaps_init(void)
> @@ -2084,6 +2127,9 @@ SYSCALL_DEFINE2(swapon, const char __use
> swap_info[prev]->next = type;
> spin_unlock(&swap_lock);
> mutex_unlock(&swapon_mutex);
> + proc_poll_event++;
> + wake_up_interruptible(&proc_poll_wait);
> +
> error = 0;
> goto out;
> bad_swap:
>
>
> --
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