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authorLinus Torvalds <torvalds@linux-foundation.org>2017-08-28 16:45:40 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-08-28 16:45:40 -0700
commit9c3a815f471a84811cf8021cf64aae3b8081dfde (patch)
tree5eea08a1005919edf7057f9da6fc18b619ce6c4a
parentb339752d054fb32863418452dff350a1086885b1 (diff)
page waitqueue: always add new entries at the end
Commit 3510ca20ece0 ("Minor page waitqueue cleanups") made the page queue code always add new waiters to the back of the queue, which helps upcoming patches to batch the wakeups for some horrid loads where the wait queues grow to thousands of entries. However, I forgot about the nasrt add_page_wait_queue() special case code that is only used by the cachefiles code. That one still continued to add the new wait queue entries at the beginning of the list. Fix it, because any sane batched wakeup will require that we don't suddenly start getting new entries at the beginning of the list that we already handled in a previous batch. [ The current code always does the whole list while holding the lock, so wait queue ordering doesn't matter for correctness, but even then it's better to add later entries at the end from a fairness standpoint ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/filemap.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 0b41c8cbeabc..65b4b6e7f7bd 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1041,7 +1041,7 @@ void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
- __add_wait_queue(q, waiter);
+ __add_wait_queue_entry_tail(q, waiter);
SetPageWaiters(page);
spin_unlock_irqrestore(&q->lock, flags);
}