linux-kernel - Re: [PATCH v2 3/4] eventfd: simplify eventfd_signal

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Message-ID: <20231122150538.6zwikm3tymnkcdxf@quack3>
Date:   Wed, 22 Nov 2023 16:05:38 +0100
From:   Jan Kara <jack@...e.cz>
To:     Christian Brauner <brauner@...nel.org>
Cc:     linux-fsdevel@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Jan Kara <jack@...e.cz>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
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Subject: Re: [PATCH v2 3/4] eventfd: simplify eventfd_signal_mask()

On Wed 22-11-23 13:48:24, Christian Brauner wrote:
> The eventfd_signal_mask() helper was introduced for io_uring and similar
> to eventfd_signal() it always passed 1 for @n. So don't bother with that
> argument at all.
> 
> Signed-off-by: Christian Brauner <brauner@...nel.org>

Nice. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/eventfd.c            | 7 ++++---
>  include/linux/eventfd.h | 5 ++---
>  io_uring/io_uring.c     | 4 ++--
>  3 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/eventfd.c b/fs/eventfd.c
> index dc9e01053235..a9a6de920fb4 100644
> --- a/fs/eventfd.c
> +++ b/fs/eventfd.c
> @@ -43,9 +43,10 @@ struct eventfd_ctx {
>  	int id;
>  };
>  
> -__u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __u64 n, __poll_t mask)
> +__u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __poll_t mask)
>  {
>  	unsigned long flags;
> +	__u64 n = 1;
>  
>  	/*
>  	 * Deadlock or stack overflow issues can happen if we recurse here
> @@ -68,7 +69,7 @@ __u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __u64 n, __poll_t mask)
>  	current->in_eventfd = 0;
>  	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
>  
> -	return n;
> +	return n == 1;
>  }
>  
>  /**
> @@ -84,7 +85,7 @@ __u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __u64 n, __poll_t mask)
>   */
>  __u64 eventfd_signal(struct eventfd_ctx *ctx)
>  {
> -	return eventfd_signal_mask(ctx, 1, 0);
> +	return eventfd_signal_mask(ctx, 0);
>  }
>  EXPORT_SYMBOL_GPL(eventfd_signal);
>  
> diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h
> index 562089431551..4f8aac7eb62a 100644
> --- a/include/linux/eventfd.h
> +++ b/include/linux/eventfd.h
> @@ -36,7 +36,7 @@ struct file *eventfd_fget(int fd);
>  struct eventfd_ctx *eventfd_ctx_fdget(int fd);
>  struct eventfd_ctx *eventfd_ctx_fileget(struct file *file);
>  __u64 eventfd_signal(struct eventfd_ctx *ctx);
> -__u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __u64 n, __poll_t mask);
> +__u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __poll_t mask);
>  int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
>  				  __u64 *cnt);
>  void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt);
> @@ -63,8 +63,7 @@ static inline int eventfd_signal(struct eventfd_ctx *ctx)
>  	return -ENOSYS;
>  }
>  
> -static inline int eventfd_signal_mask(struct eventfd_ctx *ctx, __u64 n,
> -				      unsigned mask)
> +static inline int eventfd_signal_mask(struct eventfd_ctx *ctx, unsigned mask)
>  {
>  	return -ENOSYS;
>  }
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index ed254076c723..70170a41eac4 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -558,7 +558,7 @@ static void io_eventfd_ops(struct rcu_head *rcu)
>  	int ops = atomic_xchg(&ev_fd->ops, 0);
>  
>  	if (ops & BIT(IO_EVENTFD_OP_SIGNAL_BIT))
> -		eventfd_signal_mask(ev_fd->cq_ev_fd, 1, EPOLL_URING_WAKE);
> +		eventfd_signal_mask(ev_fd->cq_ev_fd, EPOLL_URING_WAKE);
>  
>  	/* IO_EVENTFD_OP_FREE_BIT may not be set here depending on callback
>  	 * ordering in a race but if references are 0 we know we have to free
> @@ -594,7 +594,7 @@ static void io_eventfd_signal(struct io_ring_ctx *ctx)
>  		goto out;
>  
>  	if (likely(eventfd_signal_allowed())) {
> -		eventfd_signal_mask(ev_fd->cq_ev_fd, 1, EPOLL_URING_WAKE);
> +		eventfd_signal_mask(ev_fd->cq_ev_fd, EPOLL_URING_WAKE);
>  	} else {
>  		atomic_inc(&ev_fd->refs);
>  		if (!atomic_fetch_or(BIT(IO_EVENTFD_OP_SIGNAL_BIT), &ev_fd->ops))
> 
> -- 
> 2.42.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR