linux-kernel - [PATCH 4/7] fs/userfaultfd: Use exclusive waitqueue for poll()

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Message-ID: <20230905214235.320571-5-peterx@redhat.com>
Date:   Tue,  5 Sep 2023 17:42:32 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Anish Moorthy <amoorthy@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...nel.org>,
        Christian Brauner <brauner@...nel.org>, peterx@...hat.com,
        linux-fsdevel@...r.kernel.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        James Houghton <jthoughton@...gle.com>,
        Nadav Amit <nadav.amit@...il.com>
Subject: [PATCH 4/7] fs/userfaultfd: Use exclusive waitqueue for poll()

Userfaultfd is the kind of fd that does not need a wake all semantics when
wake up.  Enqueue using the new POLL_ENQUEUE_EXCLUSIVE flag.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 fs/userfaultfd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index f7fda7d0c994..9c39adc398fc 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -994,7 +994,7 @@ static __poll_t userfaultfd_poll(struct file *file, poll_table *wait)
 	struct userfaultfd_ctx *ctx = file->private_data;
 	__poll_t ret;
 
-	poll_wait(file, &ctx->fd_wqh, wait);
+	poll_wait_exclusive(file, &ctx->fd_wqh, wait);
 
 	if (!userfaultfd_is_initialized(ctx))
 		return EPOLLERR;
-- 
2.41.0