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Date:   Wed, 22 Nov 2023 16:06:43 +0100
From:   Jan Kara <jack@suse.cz>
To:     Christian Brauner <brauner@kernel.org>
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        Jan Kara <jack@suse.cz>,
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Subject: Re: [PATCH v2 4/4] eventfd: make eventfd_signal{_mask}() void
Message-ID: <20231122150643.5b57p5yxhfuxa764@quack3>
References: <20231122-vfs-eventfd-signal-v2-0-bd549b14ce0c@kernel.org>
 <20231122-vfs-eventfd-signal-v2-4-bd549b14ce0c@kernel.org>
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In-Reply-To: <20231122-vfs-eventfd-signal-v2-4-bd549b14ce0c@kernel.org>
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On Wed 22-11-23 13:48:25, Christian Brauner wrote:
> No caller care about the return value.
> 
> Signed-off-by: Christian Brauner <brauner@kernel.org>

Yup. Feel free to add:

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

								Honza

> ---
>  fs/eventfd.c            | 40 +++++++++++++++-------------------------
>  include/linux/eventfd.h | 16 +++++++---------
>  2 files changed, 22 insertions(+), 34 deletions(-)
> 
> diff --git a/fs/eventfd.c b/fs/eventfd.c
> index a9a6de920fb4..13be2fb7fc96 100644
> --- a/fs/eventfd.c
> +++ b/fs/eventfd.c
> @@ -43,10 +43,19 @@ struct eventfd_ctx {
>  	int id;
>  };
>  
> -__u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __poll_t mask)
> +/**
> + * eventfd_signal - Adds @n to the eventfd counter.
> + * @ctx: [in] Pointer to the eventfd context.
> + * @mask: [in] poll mask
> + *
> + * This function is supposed to be called by the kernel in paths that do not
> + * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
> + * value, and we signal this as overflow condition by returning a EPOLLERR
> + * to poll(2).
> + */
> +void 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
> @@ -57,37 +66,18 @@ __u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __poll_t mask)
>  	 * safe context.
>  	 */
>  	if (WARN_ON_ONCE(current->in_eventfd))
> -		return 0;
> +		return;
>  
>  	spin_lock_irqsave(&ctx->wqh.lock, flags);
>  	current->in_eventfd = 1;
> -	if (ULLONG_MAX - ctx->count < n)
> -		n = ULLONG_MAX - ctx->count;
> -	ctx->count += n;
> +	if (ctx->count < ULLONG_MAX)
> +		ctx->count++;
>  	if (waitqueue_active(&ctx->wqh))
>  		wake_up_locked_poll(&ctx->wqh, EPOLLIN | mask);
>  	current->in_eventfd = 0;
>  	spin_unlock_irqrestore(&ctx->wqh.lock, flags);
> -
> -	return n == 1;
> -}
> -
> -/**
> - * eventfd_signal - Adds @n to the eventfd counter.
> - * @ctx: [in] Pointer to the eventfd context.
> - *
> - * This function is supposed to be called by the kernel in paths that do not
> - * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
> - * value, and we signal this as overflow condition by returning a EPOLLERR
> - * to poll(2).
> - *
> - * Returns the amount by which the counter was incremented.
> - */
> -__u64 eventfd_signal(struct eventfd_ctx *ctx)
> -{
> -	return eventfd_signal_mask(ctx, 0);
>  }
> -EXPORT_SYMBOL_GPL(eventfd_signal);
> +EXPORT_SYMBOL_GPL(eventfd_signal_mask);
>  
>  static void eventfd_free_ctx(struct eventfd_ctx *ctx)
>  {
> diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h
> index 4f8aac7eb62a..fea7c4eb01d6 100644
> --- a/include/linux/eventfd.h
> +++ b/include/linux/eventfd.h
> @@ -35,8 +35,7 @@ void eventfd_ctx_put(struct eventfd_ctx *ctx);
>  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, __poll_t mask);
> +void 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);
> @@ -58,14 +57,8 @@ static inline struct eventfd_ctx *eventfd_ctx_fdget(int fd)
>  	return ERR_PTR(-ENOSYS);
>  }
>  
> -static inline int eventfd_signal(struct eventfd_ctx *ctx)
> +static inline void eventfd_signal_mask(struct eventfd_ctx *ctx, unsigned mask)
>  {
> -	return -ENOSYS;
> -}
> -
> -static inline int eventfd_signal_mask(struct eventfd_ctx *ctx, unsigned mask)
> -{
> -	return -ENOSYS;
>  }
>  
>  static inline void eventfd_ctx_put(struct eventfd_ctx *ctx)
> @@ -91,5 +84,10 @@ static inline void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
>  
>  #endif
>  
> +static inline void eventfd_signal(struct eventfd_ctx *ctx)
> +{
> +	eventfd_signal_mask(ctx, 0);
> +}
> +
>  #endif /* _LINUX_EVENTFD_H */
>  
> 
> -- 
> 2.42.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR