[PATCH 2/3] epoll: loosen irq safety in ep_poll_callback()

[Roman Penyaev]

Callers of the ep_poll_callback() (all set of wake_up_*poll()) disable
interrupts, so no need to save/restore irq flags.

Signed-off-by: Roman Penyaev <rpeny...@suse.de>
Cc: Davidlohr Bueso <dbu...@suse.de>
Cc: Jason Baron <jba...@akamai.com>
Cc: Al Viro <v...@zeniv.linux.org.uk>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: linux-fsde...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 fs/eventpoll.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 3627c2e07149..ea0025e77519 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1124,13 +1124,15 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file, 
int tfd,
 static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, 
void *key)
 {
        int pwake = 0;
-       unsigned long flags;
        struct epitem *epi = ep_item_from_wait(wait);
        struct eventpoll *ep = epi->ep;
        __poll_t pollflags = key_to_poll(key);
        int ewake = 0;
 
-       spin_lock_irqsave(&ep->wq.lock, flags);
+       /* Interrupts are disabled by the wake_up_*poll() callers */
+       lockdep_assert_irqs_disabled();
+
+       spin_lock(&ep->wq.lock);
 
        ep_set_busy_poll_napi_id(epi);
 
@@ -1207,7 +1209,7 @@ static int ep_poll_callback(wait_queue_entry_t *wait, 
unsigned mode, int sync, v
                pwake++;
 
 out_unlock:
-       spin_unlock_irqrestore(&ep->wq.lock, flags);
+       spin_unlock(&ep->wq.lock);
 
        /* We have to call this outside the lock */
        if (pwake)
-- 
2.19.1