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| author | Kay Sievers <kay.sievers@vrfy.org> | 2010-10-26 14:22:06 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-26 16:52:11 -0700 |
| commit | 66d7dd518ae413a383ab2c6c263cc30617329842 (patch) | |
| tree | 8e16f734aebba063e0df052825ac375aefeeab5a /mm/swapfile.c | |
| parent | e1ca7788dec6773b1a2bce51b7141948f2b8bccf (diff) | |
| download | linux-66d7dd518ae413a383ab2c6c263cc30617329842.tar.gz | |
/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: 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>
Diffstat (limited to 'mm/swapfile.c')
| -rw-r--r-- | mm/swapfile.c | 49 |
1 files changed, 48 insertions, 1 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c index 9fc7bac7db0c..67ddaaf98c74 100644 --- 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 +59,10 @@ 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: |