On 07/23, Linus Torvalds wrote: > > But I'll walk over my patch mentally one more time. Here's the current > version, anyway. Both patches look correct to me, feel free to add Reviewed-by: Oleg Nesterov <oleg@xxxxxxxxxx> > @@ -1013,18 +1014,40 @@ static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, > if (wait_page->bit_nr != key->bit_nr) > return 0; > > + /* Stop walking if it's locked */ > + if (wait->flags & WQ_FLAG_EXCLUSIVE) { > + if (test_and_set_bit(key->bit_nr, &key->page->flags)) > + return -1; > + } else { > + if (test_bit(key->bit_nr, &key->page->flags)) > + return -1; > + } not sure this makes any sense, but this looks like another user of trylock_page_bit_common(), see the patch below on top of 1/2. Oleg. --- mm/filemap.c~ 2020-07-24 17:09:34.728133846 +0200 +++ mm/filemap.c 2020-07-24 17:23:52.279185374 +0200 @@ -1000,6 +1000,14 @@ wait_queue_entry_t wait; }; +static int trylock_page_bit_common(struct page *page, int bit_nr, + struct wait_queue_entry *wait) +{ + return wait->flags & WQ_FLAG_EXCLUSIVE ? + !test_and_set_bit(bit_nr, &page->flags) : + !test_bit(bit_nr, &page->flags); +} + static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg) { int ret; @@ -1015,13 +1023,8 @@ return 0; /* Stop walking if it's locked */ - if (wait->flags & WQ_FLAG_EXCLUSIVE) { - if (test_and_set_bit(key->bit_nr, &key->page->flags)) - return -1; - } else { - if (test_bit(key->bit_nr, &key->page->flags)) - return -1; - } + if (!trylock_page_bit_common(key->page, key->bit_nr, wait)) + return -1; /* * Let the waiter know we have done the page flag @@ -1126,14 +1129,6 @@ */ }; -static inline int trylock_page_bit_common(struct page *page, int bit_nr, - enum behavior behavior) -{ - return behavior == EXCLUSIVE ? - !test_and_set_bit(bit_nr, &page->flags) : - !test_bit(bit_nr, &page->flags); -} - static inline int wait_on_page_bit_common(wait_queue_head_t *q, struct page *page, int bit_nr, int state, enum behavior behavior) { @@ -1170,7 +1165,7 @@ */ spin_lock_irq(&q->lock); SetPageWaiters(page); - if (!trylock_page_bit_common(page, bit_nr, behavior)) + if (!trylock_page_bit_common(page, bit_nr, wait)) __add_wait_queue_entry_tail(q, wait); spin_unlock_irq(&q->lock);