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Fri, 05 Jun 2026 23:11:24 -0700 (PDT) From: Askar Safin To: linux-fsdevel@vger.kernel.org, Christian Brauner , Alexander Viro , Jan Kara Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, netdev@vger.kernel.org, fuse-devel@lists.linux.dev, ltp@lists.linux.it, Linus Torvalds , Matthew Wilcox , Jens Axboe , Christoph Hellwig , David Howells , Andrew Morton , David Hildenbrand , Pedro Falcato , Miklos Szeredi , Andy Lutomirski , Collin Funk , David Laight , Stefan Metzmacher , Steven Rostedt , The 8472 , Willy Tarreau , Joanne Koong , patches@lists.linux.dev Subject: [PATCH 1/5] vmsplice: open-code do_writev and do_readv Date: Sat, 6 Jun 2026 06:10:27 +0000 Message-ID: <20260606061031.3744880-2-safinaskar@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260606061031.3744880-1-safinaskar@gmail.com> References: <20260606061031.3744880-1-safinaskar@gmail.com> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit My previous vmsplice patch did the following mistake: I did "CLASS(fd, f)(fd)", then did some checks on resulting "struct file", then passed numeric (!) file descriptor to a function. This is somewhat okay in this particular case, but I still think this is code smell, so I fix this by open-coding do_writev and do_readv. Also I insert a comment to warn other developers to keep do_writev and do_readv in sync with vmsplice(2). Signed-off-by: Askar Safin --- fs/read_write.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/fs/read_write.c b/fs/read_write.c index 1e5444f4d..e224e7cb8 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -1070,6 +1070,7 @@ static ssize_t vfs_writev(struct file *file, const struct iovec __user *vec, static ssize_t do_readv(unsigned long fd, const struct iovec __user *vec, unsigned long vlen, rwf_t flags) { + /* All future changes to this function should be kept in sync with vmsplice(2). */ CLASS(fd_pos, f)(fd); ssize_t ret = -EBADF; @@ -1093,6 +1094,7 @@ static ssize_t do_readv(unsigned long fd, const struct iovec __user *vec, static ssize_t do_writev(unsigned long fd, const struct iovec __user *vec, unsigned long vlen, rwf_t flags) { + /* All future changes to this function should be kept in sync with vmsplice(2). */ CLASS(fd_pos, f)(fd); ssize_t ret = -EBADF; @@ -1226,14 +1228,24 @@ SYSCALL_DEFINE4(vmsplice, unsigned long, fd, const struct iovec __user *, vec, if (fd_empty(f)) return -EBADF; - /* We do do_writev/do_readv, so it is okay to pass "false" here */ + /* We do vfs_writev/vfs_readv, so it is okay to pass "false" here */ if (!get_pipe_info(fd_file(f), /* for_splice = */ false)) return -EBADF; - if (fd_file(f)->f_mode & FMODE_WRITE) - return do_writev(fd, vec, vlen, (flags & SPLICE_F_NONBLOCK) ? RWF_NOWAIT : 0); - else - return do_readv(fd, vec, vlen, (flags & SPLICE_F_NONBLOCK) ? RWF_NOWAIT : 0); + if (fd_file(f)->f_mode & FMODE_WRITE) { + ssize_t ret = vfs_writev(fd_file(f), vec, vlen, NULL, (flags & SPLICE_F_NONBLOCK) ? RWF_NOWAIT : 0); + if (ret > 0) + add_wchar(current, ret); + inc_syscw(current); + return ret; + } else { + ssize_t ret = vfs_readv(fd_file(f), vec, vlen, NULL, (flags & SPLICE_F_NONBLOCK) ? RWF_NOWAIT : 0); + + if (ret > 0) + add_rchar(current, ret); + inc_syscr(current); + return ret; + } } /* -- 2.47.3