From 792060de8b3e9ca11fab4afc0c3c5927186152a2 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 26 Feb 2024 16:43:01 -0700 Subject: io_uring/net: improve the usercopy for sendmsg/recvmsg We're spending a considerable amount of the sendmsg/recvmsg time just copying in the message header. And for provided buffers, the known single entry iovec. Be a bit smarter about it and enable/disable user access around our copying. In a test case that does both sendmsg and recvmsg, the runtime before this change (averaged over multiple runs, very stable times however): Kernel Time Diff ==================================== -git 4720 usec -git+commit 4311 usec -8.7% and looking at a profile diff, we see the following: 0.25% +9.33% [kernel.kallsyms] [k] _copy_from_user 4.47% -3.32% [kernel.kallsyms] [k] __io_msg_copy_hdr.constprop.0 where we drop more than 9% of _copy_from_user() time, and consequently add time to __io_msg_copy_hdr() where the copies are now attributed to, but with a net win of 6%. In comparison, the same test case with send/recv runs in 3745 usec, which is (expectedly) still quite a bit faster. But at least sendmsg/recvmsg is now only ~13% slower, where it was ~21% slower before. Signed-off-by: Jens Axboe --- io_uring/net.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) (limited to 'io_uring') diff --git a/io_uring/net.c b/io_uring/net.c index 7a07c5563d66..83fba2882720 100644 --- a/io_uring/net.c +++ b/io_uring/net.c @@ -255,27 +255,42 @@ static int io_msg_copy_hdr(struct io_kiocb *req, struct io_async_msghdr *iomsg, struct io_sr_msg *sr = io_kiocb_to_cmd(req, struct io_sr_msg); int ret; - if (copy_from_user(msg, sr->umsg, sizeof(*sr->umsg))) + if (!user_access_begin(sr->umsg, sizeof(*sr->umsg))) return -EFAULT; + ret = -EFAULT; + unsafe_get_user(msg->msg_name, &sr->umsg->msg_name, ua_end); + unsafe_get_user(msg->msg_namelen, &sr->umsg->msg_namelen, ua_end); + unsafe_get_user(msg->msg_iov, &sr->umsg->msg_iov, ua_end); + unsafe_get_user(msg->msg_iovlen, &sr->umsg->msg_iovlen, ua_end); + unsafe_get_user(msg->msg_control, &sr->umsg->msg_control, ua_end); + unsafe_get_user(msg->msg_controllen, &sr->umsg->msg_controllen, ua_end); + msg->msg_flags = 0; + if (req->flags & REQ_F_BUFFER_SELECT) { if (msg->msg_iovlen == 0) { sr->len = iomsg->fast_iov[0].iov_len = 0; iomsg->fast_iov[0].iov_base = NULL; iomsg->free_iov = NULL; } else if (msg->msg_iovlen > 1) { - return -EINVAL; + ret = -EINVAL; + goto ua_end; } else { - if (copy_from_user(iomsg->fast_iov, msg->msg_iov, - sizeof(*msg->msg_iov))) - return -EFAULT; + /* we only need the length for provided buffers */ + if (!access_ok(&msg->msg_iov[0].iov_len, sizeof(__kernel_size_t))) + goto ua_end; + unsafe_get_user(iomsg->fast_iov[0].iov_len, + &msg->msg_iov[0].iov_len, ua_end); sr->len = iomsg->fast_iov[0].iov_len; iomsg->free_iov = NULL; } - - return 0; + ret = 0; +ua_end: + user_access_end(); + return ret; } + user_access_end(); iomsg->free_iov = iomsg->fast_iov; ret = __import_iovec(ddir, msg->msg_iov, msg->msg_iovlen, UIO_FASTIOV, &iomsg->free_iov, &iomsg->msg.msg_iter, false); -- cgit v1.2.3