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[79.129.48.248]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43d200fae4asm126660125e9.27.2025.03.18.00.24.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Mar 2025 00:24:53 -0700 (PDT) Message-ID: <566c700c-d3d5-4899-8de1-87092e76310c@gmail.com> Date: Tue, 18 Mar 2025 07:25:51 +0000 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v4 4/5] btrfs: ioctl: introduce btrfs_uring_import_iovec() To: Sidong Yang , Jens Axboe Cc: Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, io-uring@vger.kernel.org References: <20250317135742.4331-1-sidong.yang@furiosa.ai> <20250317135742.4331-5-sidong.yang@furiosa.ai> <3a883e1e-d822-4c89-a7b0-f8802b8cc261@kernel.dk> Content-Language: en-US From: Pavel Begunkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/18/25 01:58, Sidong Yang wrote: > On Mon, Mar 17, 2025 at 09:40:05AM -0600, Jens Axboe wrote: >> On 3/17/25 7:57 AM, Sidong Yang wrote: >>> This patch introduces btrfs_uring_import_iovec(). In encoded read/write >>> with uring cmd, it uses import_iovec without supporting fixed buffer. >>> btrfs_using_import_iovec() could use fixed buffer if cmd flags has >>> IORING_URING_CMD_FIXED. >>> >>> Signed-off-by: Sidong Yang >>> --- >>> fs/btrfs/ioctl.c | 32 ++++++++++++++++++++++++-------- >>> 1 file changed, 24 insertions(+), 8 deletions(-) >>> >>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c >>> index 6c18bad53cd3..a7b52fd99059 100644 >>> --- a/fs/btrfs/ioctl.c >>> +++ b/fs/btrfs/ioctl.c >>> @@ -4802,6 +4802,28 @@ struct btrfs_uring_encoded_data { >>> struct iov_iter iter; >>> }; >>> >>> +static int btrfs_uring_import_iovec(struct io_uring_cmd *cmd, >>> + unsigned int issue_flags, int rw) >>> +{ >>> + struct btrfs_uring_encoded_data *data = >>> + io_uring_cmd_get_async_data(cmd)->op_data; >>> + int ret; >>> + >>> + if (cmd && (cmd->flags & IORING_URING_CMD_FIXED)) { >>> + data->iov = NULL; >>> + ret = io_uring_cmd_import_fixed_vec(cmd, data->args.iov, >>> + data->args.iovcnt, >>> + ITER_DEST, issue_flags, >>> + &data->iter); >>> + } else { >>> + data->iov = data->iovstack; >>> + ret = import_iovec(rw, data->args.iov, data->args.iovcnt, >>> + ARRAY_SIZE(data->iovstack), &data->iov, >>> + &data->iter); >>> + } >>> + return ret; >>> +} >> >> How can 'cmd' be NULL here? > > It seems that there is no checkes for 'cmd' before and it works same as before. > But I think it's better to add a check in function start for safety. The check goes two lines after you already dereferenced it, and it seems to be called from io_uring cmd specific code. The null check only adds to confusion. -- Pavel Begunkov