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Tue, 18 Mar 2025 00:55:53 -0700 (PDT) Received: from sidongui-MacBookPro.local ([221.148.76.1]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7371169c3desm8846112b3a.155.2025.03.18.00.55.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Mar 2025 00:55:52 -0700 (PDT) Date: Tue, 18 Mar 2025 16:55:43 +0900 From: Sidong Yang To: Pavel Begunkov Cc: Jens Axboe , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, io-uring@vger.kernel.org Subject: Re: [RFC PATCH v4 4/5] btrfs: ioctl: introduce btrfs_uring_import_iovec() Message-ID: References: <20250317135742.4331-1-sidong.yang@furiosa.ai> <20250317135742.4331-5-sidong.yang@furiosa.ai> <3a883e1e-d822-4c89-a7b0-f8802b8cc261@kernel.dk> <566c700c-d3d5-4899-8de1-87092e76310c@gmail.com> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <566c700c-d3d5-4899-8de1-87092e76310c@gmail.com> On Tue, Mar 18, 2025 at 07:25:51AM +0000, Pavel Begunkov wrote: > 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. You mean 'cmd' already dereferenced for async_data. Is it okay to just delete code checking 'cmd' like below? if (cmd->flags & IORING_URING_CMD_FIXED) { Thanks, Sidong > > -- > Pavel Begunkov >