linux-kernel - [PATCH 5.2 081/131] dax: Fix missed wakeup in put_unlocked

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Message-Id: <20190805124957.361969657@linuxfoundation.org>
Date:   Mon,  5 Aug 2019 15:02:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jan Kara <jack@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH 5.2 081/131] dax: Fix missed wakeup in put_unlocked_entry()

From: Jan Kara <jack@...e.cz>

commit 61c30c98ef17e5a330d7bb8494b78b3d6dffe9b8 upstream.

The condition checking whether put_unlocked_entry() needs to wake up
following waiter got broken by commit 23c84eb78375 ("dax: Fix missed
wakeup with PMD faults"). We need to wake the waiter whenever the passed
entry is valid (i.e., non-NULL and not special conflict entry). This
could lead to processes never being woken up when waiting for entry
lock. Fix the condition.

Cc: <stable@...r.kernel.org>
Link: http://lore.kernel.org/r/20190729120228.GC17833@quack2.suse.cz
Fixes: 23c84eb78375 ("dax: Fix missed wakeup with PMD faults")
Signed-off-by: Jan Kara <jack@...e.cz>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/dax.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/dax.c
+++ b/fs/dax.c
@@ -267,7 +267,7 @@ static void wait_entry_unlocked(struct x
 static void put_unlocked_entry(struct xa_state *xas, void *entry)
 {
 	/* If we were the only waiter woken, wake the next one */
-	if (entry && dax_is_conflict(entry))
+	if (entry && !dax_is_conflict(entry))
 		dax_wake_entry(xas, entry, false);
 }