[PATCH RESEND v2 28/30] mm/swapfile: let procfs own the wait queue of /proc/swaps

[Christian Brauner]

swaps_poll() sleeps the poller on a queue of its own. procfs owns the
queue poll() uses now, so leave the poll_wait() to it and wake its
pollers when a swap area comes or goes.

Signed-off-by: Christian Brauner (Amutable) <brauner at kernel.org>
---
 mm/swapfile.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index ee4868ecc3a7..1d063a1cef43 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -111,7 +111,7 @@ static struct kmem_cache *swap_table_cachep;
 /* Protects si->swap_file for /proc/swaps usage */
 static DEFINE_MUTEX(swapon_mutex);
 
-static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait);
+static struct proc_dir_entry *proc_swaps;
 /* Activity counter to indicate that a swapon or swapoff has occurred */
 static atomic_t proc_poll_event = ATOMIC_INIT(0);
 
@@ -3307,7 +3307,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 
 	err = 0;
 	atomic_inc(&proc_poll_event);
-	wake_up_interruptible(&proc_poll_wait);
+	proc_poll_notify(proc_swaps);
 
 out_dput:
 	filp_close(victim, NULL);
@@ -3319,8 +3319,6 @@ static __poll_t swaps_poll(struct file *file, poll_table *wait)
 {
 	struct seq_file *seq = file->private_data;
 
-	poll_wait(file, &proc_poll_wait, wait);
-
 	if (seq->poll_event != atomic_read(&proc_poll_event)) {
 		seq->poll_event = atomic_read(&proc_poll_event);
 		return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
@@ -3428,7 +3426,7 @@ static const struct proc_ops swaps_proc_ops = {
 
 static int __init procswaps_init(void)
 {
-	proc_create("swaps", 0, NULL, &swaps_proc_ops);
+	proc_swaps = proc_create("swaps", 0, NULL, &swaps_proc_ops);
 	return 0;
 }
 __initcall(procswaps_init);
@@ -3907,7 +3905,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 
 	mutex_unlock(&swapon_mutex);
 	atomic_inc(&proc_poll_event);
-	wake_up_interruptible(&proc_poll_wait);
+	proc_poll_notify(proc_swaps);
 
 	error = 0;
 	goto out;

-- 
2.53.0