The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 25bbe21bf427a81b8e3ccd480ea0e1d940256156 Mon Sep 17 00:00:00 2001
From: Matthew Wilcox willy@infradead.org Date: Fri, 16 Nov 2018 15:50:02 -0500 Subject: [PATCH] dax: Avoid losing wakeup in dax_lock_mapping_entry
After calling get_unlocked_entry(), you have to call put_unlocked_entry() to avoid subsequent waiters losing wakeups.
Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()") Cc: stable@vger.kernel.org Signed-off-by: Matthew Wilcox willy@infradead.org
diff --git a/fs/dax.c b/fs/dax.c index cf2394e2bf4b..9bcce89ea18e 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -391,6 +391,7 @@ bool dax_lock_mapping_entry(struct page *page) rcu_read_unlock(); entry = get_unlocked_entry(&xas); xas_unlock_irq(&xas); + put_unlocked_entry(&xas, entry); rcu_read_lock(); continue; }