Re: [PATCH] io_uring: fix linked command file table usage

[Pavel Begunkov <asml.silence@gmail.com>]

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FYI, for-next

fs/io_uring.c: In function ‘io_epoll_ctl’:
fs/io_uring.c:2661:22: error: ‘IO_WQ_WORK_NEEDS_FILES’ undeclared (first use in
this function)
 2661 |   req->work.flags |= IO_WQ_WORK_NEEDS_FILES;
      |                      ^~~~~~~~~~~~~~~~~~~~~~
fs/io_uring.c:2661:22: note: each undeclared identifier is reported only once
for each function it appears in
make[1]: *** [scripts/Makefile.build:266: fs/io_uring.o] Error 1
make: *** [Makefile:1693: fs] Error 2


On 29/01/2020 23:49, Jens Axboe wrote:
> We're not consistent in how the file table is grabbed and assigned if we
> have a command linked that requires the use of it.
> 
> Add ->file_table to the io_op_defs[] array, and use that to determine
> when to grab the table instead of having the handlers set it if they
> need to defer. This also means we can kill the IO_WQ_WORK_NEEDS_FILES
> flag. We always initialize work->files, so io-wq can just check for
> that.
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> 
> ---
> 
> diff --git a/fs/io-wq.c b/fs/io-wq.c
> index f7eb577ccd2d..cb60a42b9fdf 100644
> --- a/fs/io-wq.c
> +++ b/fs/io-wq.c
> @@ -476,8 +476,7 @@ static void io_worker_handle_work(struct io_worker *worker)
>  		if (work->flags & IO_WQ_WORK_CB)
>  			work->func(&work);
>  
> -		if ((work->flags & IO_WQ_WORK_NEEDS_FILES) &&
> -		    current->files != work->files) {
> +		if (work->files && current->files != work->files) {
>  			task_lock(current);
>  			current->files = work->files;
>  			task_unlock(current);
> diff --git a/fs/io-wq.h b/fs/io-wq.h
> index c42602c58c56..50b3378febf2 100644
> --- a/fs/io-wq.h
> +++ b/fs/io-wq.h
> @@ -7,7 +7,6 @@ enum {
>  	IO_WQ_WORK_CANCEL	= 1,
>  	IO_WQ_WORK_HAS_MM	= 2,
>  	IO_WQ_WORK_HASHED	= 4,
> -	IO_WQ_WORK_NEEDS_FILES	= 16,
>  	IO_WQ_WORK_UNBOUND	= 32,
>  	IO_WQ_WORK_INTERNAL	= 64,
>  	IO_WQ_WORK_CB		= 128,
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 8bcf0538e2e1..0d8d0e217847 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -603,6 +603,8 @@ struct io_op_def {
>  	unsigned		unbound_nonreg_file : 1;
>  	/* opcode is not supported by this kernel */
>  	unsigned		not_supported : 1;
> +	/* needs file table */
> +	unsigned		file_table : 1;
>  };
>  
>  static const struct io_op_def io_op_defs[] = {
> @@ -661,6 +663,7 @@ static const struct io_op_def io_op_defs[] = {
>  		.needs_mm		= 1,
>  		.needs_file		= 1,
>  		.unbound_nonreg_file	= 1,
> +		.file_table		= 1,
>  	},
>  	[IORING_OP_ASYNC_CANCEL] = {},
>  	[IORING_OP_LINK_TIMEOUT] = {
> @@ -679,12 +682,15 @@ static const struct io_op_def io_op_defs[] = {
>  	[IORING_OP_OPENAT] = {
>  		.needs_file		= 1,
>  		.fd_non_neg		= 1,
> +		.file_table		= 1,
>  	},
>  	[IORING_OP_CLOSE] = {
>  		.needs_file		= 1,
> +		.file_table		= 1,
>  	},
>  	[IORING_OP_FILES_UPDATE] = {
>  		.needs_mm		= 1,
> +		.file_table		= 1,
>  	},
>  	[IORING_OP_STATX] = {
>  		.needs_mm		= 1,
> @@ -720,6 +726,7 @@ static const struct io_op_def io_op_defs[] = {
>  	[IORING_OP_OPENAT2] = {
>  		.needs_file		= 1,
>  		.fd_non_neg		= 1,
> +		.file_table		= 1,
>  	},
>  };
>  
> @@ -732,6 +739,7 @@ static void io_queue_linked_timeout(struct io_kiocb *req);
>  static int __io_sqe_files_update(struct io_ring_ctx *ctx,
>  				 struct io_uring_files_update *ip,
>  				 unsigned nr_args);
> +static int io_grab_files(struct io_kiocb *req);
>  
>  static struct kmem_cache *req_cachep;
>  
> @@ -2568,10 +2576,8 @@ static int io_openat2(struct io_kiocb *req, struct io_kiocb **nxt,
>  	struct file *file;
>  	int ret;
>  
> -	if (force_nonblock) {
> -		req->work.flags |= IO_WQ_WORK_NEEDS_FILES;
> +	if (force_nonblock)
>  		return -EAGAIN;
> -	}
>  
>  	ret = build_open_flags(&req->open.how, &op);
>  	if (ret)
> @@ -2797,10 +2803,8 @@ static int io_close(struct io_kiocb *req, struct io_kiocb **nxt,
>  		return ret;
>  
>  	/* if the file has a flush method, be safe and punt to async */
> -	if (req->close.put_file->f_op->flush && !io_wq_current_is_worker()) {
> -		req->work.flags |= IO_WQ_WORK_NEEDS_FILES;
> +	if (req->close.put_file->f_op->flush && !io_wq_current_is_worker())
>  		goto eagain;
> -	}
>  
>  	/*
>  	 * No ->flush(), safely close from here and just punt the
> @@ -3244,7 +3248,6 @@ static int io_accept(struct io_kiocb *req, struct io_kiocb **nxt,
>  	ret = __io_accept(req, nxt, force_nonblock);
>  	if (ret == -EAGAIN && force_nonblock) {
>  		req->work.func = io_accept_finish;
> -		req->work.flags |= IO_WQ_WORK_NEEDS_FILES;
>  		io_put_req(req);
>  		return -EAGAIN;
>  	}
> @@ -3967,10 +3970,8 @@ static int io_files_update(struct io_kiocb *req, bool force_nonblock)
>  	struct io_uring_files_update up;
>  	int ret;
>  
> -	if (force_nonblock) {
> -		req->work.flags |= IO_WQ_WORK_NEEDS_FILES;
> +	if (force_nonblock)
>  		return -EAGAIN;
> -	}
>  
>  	up.offset = req->files_update.offset;
>  	up.fds = req->files_update.arg;
> @@ -3991,6 +3992,12 @@ static int io_req_defer_prep(struct io_kiocb *req,
>  {
>  	ssize_t ret = 0;
>  
> +	if (io_op_defs[req->opcode].file_table) {
> +		ret = io_grab_files(req);
> +		if (unlikely(ret))
> +			return ret;
> +	}
> +
>  	io_req_work_grab_env(req, &io_op_defs[req->opcode]);
>  
>  	switch (req->opcode) {
> @@ -4424,6 +4431,8 @@ static int io_grab_files(struct io_kiocb *req)
>  	int ret = -EBADF;
>  	struct io_ring_ctx *ctx = req->ctx;
>  
> +	if (req->work.files)
> +		return 0;
>  	if (!ctx->ring_file)
>  		return -EBADF;
>  
> @@ -4542,7 +4551,7 @@ static void __io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>  	if (ret == -EAGAIN && (!(req->flags & REQ_F_NOWAIT) ||
>  	    (req->flags & REQ_F_MUST_PUNT))) {
>  punt:
> -		if (req->work.flags & IO_WQ_WORK_NEEDS_FILES) {
> +		if (io_op_defs[req->opcode].file_table) {
>  			ret = io_grab_files(req);
>  			if (ret)
>  				goto err;
> 

-- 
Pavel Begunkov


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