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Subject[PATCH 4.19 099/110] dax: Avoid losing wakeup in dax_lock_mapping_entry
Date
4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthew Wilcox <willy@infradead.org>

commit 25bbe21bf427a81b8e3ccd480ea0e1d940256156 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/dax.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/fs/dax.c
+++ b/fs/dax.c
@@ -217,6 +217,9 @@ static inline void *unlock_slot(struct a
return (void *)entry;
}

+static void put_unlocked_mapping_entry(struct address_space *mapping,
+ pgoff_t index, void *entry);
+
/*
* Lookup entry in radix tree, wait for it to become unlocked if it is
* exceptional entry and return it. The caller must call
@@ -256,8 +259,10 @@ static void *__get_unlocked_mapping_entr
revalidate = wait_fn();
finish_wait(wq, &ewait.wait);
xa_lock_irq(&mapping->i_pages);
- if (revalidate)
+ if (revalidate) {
+ put_unlocked_mapping_entry(mapping, index, entry);
return ERR_PTR(-EAGAIN);
+ }
}
}


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