[Qemu-devel] [PATCH 6/7] userfaultfd: Revert "userfaultfd: waitqueue: add nr wake parameter to __wake_up_locked_key"

[Andrea Arcangeli]

This reverts commit 855c5a9026b0fce58c8de5382ef8ce00f74c1331 and
adapts fs/userfaultfd.c to use the old version of that function.

It didn't look robust to call __wake_up_common with "nr == 1" when we
absolutely require wakeall semantics, but we've full control of what
we insert in the two waitqueue heads of the blocked userfaults. No
exclusive waitqueue risks to be inserted into those two waitqueue
heads so we can as well stick to "nr == 1" of the old code and we can
rely purely on the fact no waitqueue inserted in one of the two
waitqueue heads we must enforce as wakeall, has wait->flags
WQ_FLAG_EXCLUSIVE set.

Signed-off-by: Andrea Arcangeli <address@hidden>
---
 fs/userfaultfd.c     | 8 ++++----
 include/linux/wait.h | 5 ++---
 kernel/sched/wait.c  | 7 +++----
 net/sunrpc/sched.c   | 2 +-
 4 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index a66c4be..e601dd8 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -467,8 +467,8 @@ static int userfaultfd_release(struct inode *inode, struct 
file *file)
         * the fault_*wqh.
         */
        spin_lock(&ctx->fault_pending_wqh.lock);
-       __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, 0, &range);
-       __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, 0, &range);
+       __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range);
+       __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range);
        spin_unlock(&ctx->fault_pending_wqh.lock);
 
        wake_up_poll(&ctx->fd_wqh, POLLHUP);
@@ -652,10 +652,10 @@ static void __wake_userfault(struct userfaultfd_ctx *ctx,
        spin_lock(&ctx->fault_pending_wqh.lock);
        /* wake all in the range and autoremove */
        if (waitqueue_active(&ctx->fault_pending_wqh))
-               __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, 0,
+               __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL,
                                     range);
        if (waitqueue_active(&ctx->fault_wqh))
-               __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, 0, range);
+               __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, range);
        spin_unlock(&ctx->fault_pending_wqh.lock);
 }
 
diff --git a/include/linux/wait.h b/include/linux/wait.h
index cf884cf..2db8334 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -147,8 +147,7 @@ __remove_wait_queue(wait_queue_head_t *head, wait_queue_t 
*old)
 
 typedef int wait_bit_action_f(struct wait_bit_key *);
 void __wake_up(wait_queue_head_t *q, unsigned int mode, int nr, void *key);
-void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, int nr,
-                         void *key);
+void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, void *key);
 void __wake_up_sync_key(wait_queue_head_t *q, unsigned int mode, int nr, void 
*key);
 void __wake_up_locked(wait_queue_head_t *q, unsigned int mode, int nr);
 void __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr);
@@ -180,7 +179,7 @@ wait_queue_head_t *bit_waitqueue(void *, int);
 #define wake_up_poll(x, m)                                             \
        __wake_up(x, TASK_NORMAL, 1, (void *) (m))
 #define wake_up_locked_poll(x, m)                                      \
-       __wake_up_locked_key((x), TASK_NORMAL, 1, (void *) (m))
+       __wake_up_locked_key((x), TASK_NORMAL, (void *) (m))
 #define wake_up_interruptible_poll(x, m)                               \
        __wake_up(x, TASK_INTERRUPTIBLE, 1, (void *) (m))
 #define wake_up_interruptible_sync_poll(x, m)                          \
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 6da208dd2..852143a 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -106,10 +106,9 @@ void __wake_up_locked(wait_queue_head_t *q, unsigned int 
mode, int nr)
 }
 EXPORT_SYMBOL_GPL(__wake_up_locked);
 
-void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, int nr,
-                         void *key)
+void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, void *key)
 {
-       __wake_up_common(q, mode, nr, 0, key);
+       __wake_up_common(q, mode, 1, 0, key);
 }
 EXPORT_SYMBOL_GPL(__wake_up_locked_key);
 
@@ -284,7 +283,7 @@ void abort_exclusive_wait(wait_queue_head_t *q, 
wait_queue_t *wait,
        if (!list_empty(&wait->task_list))
                list_del_init(&wait->task_list);
        else if (waitqueue_active(q))
-               __wake_up_locked_key(q, mode, 1, key);
+               __wake_up_locked_key(q, mode, key);
        spin_unlock_irqrestore(&q->lock, flags);
 }
 EXPORT_SYMBOL(abort_exclusive_wait);
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index b140c09..337ca85 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -297,7 +297,7 @@ static int rpc_complete_task(struct rpc_task *task)
        clear_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
        ret = atomic_dec_and_test(&task->tk_count);
        if (waitqueue_active(wq))
-               __wake_up_locked_key(wq, TASK_NORMAL, 1, &k);
+               __wake_up_locked_key(wq, TASK_NORMAL, &k);
        spin_unlock_irqrestore(&wq->lock, flags);
        return ret;
 }