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Miller" , Jakub Kicinski , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Stefan Metzmacher Subject: [PATCH v3 2/4] io_uring: openat directly into fixed fd table Date: Sat, 21 Aug 2021 16:52:38 +0100 Message-Id: X-Mailer: git-send-email 2.32.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Instead of opening a file into a process's file table as usual and then registering the fd within io_uring, some users may want to skip the first step and place it directly into io_uring's fixed file table. This patch adds such a capability for IORING_OP_OPENAT and IORING_OP_OPENAT2. The behaviour is controlled by setting sqe->file_index, where 0 implies the old behaviour. If non-zero value is specified, then it will behave as described and place the file into a fixed file slot sqe->file_index - 1. A file table should be already created, the slot should be valid and empty, otherwise the operation will fail. Keep the error codes consistent with IORING_OP_FILES_UPDATE, ENXIO and EINVAL on inappropriate fixed tables, and return EBADF on collision with already registered file. Note: we can't use IOSQE_FIXED_FILE to switch between modes, because accept takes a file, and it already uses the flag with a different meaning. Suggested-by: Josh Triplett Signed-off-by: Pavel Begunkov --- fs/io_uring.c | 82 +++++++++++++++++++++++++++++++---- include/uapi/linux/io_uring.h | 5 ++- 2 files changed, 78 insertions(+), 9 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 0fb75aa72b69..b8ef5ac1f90d 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1063,6 +1063,9 @@ static void io_req_task_queue(struct io_kiocb *req); static void io_submit_flush_completions(struct io_ring_ctx *ctx); static int io_req_prep_async(struct io_kiocb *req); +static int io_install_fixed_file(struct io_kiocb *req, struct file *file, + unsigned int issue_flags); + static struct kmem_cache *req_cachep; static const struct file_operations io_uring_fops; @@ -3815,11 +3818,12 @@ static int io_fallocate(struct io_kiocb *req, unsigned int issue_flags) static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) { const char __user *fname; + unsigned index; int ret; if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL)) return -EINVAL; - if (unlikely(sqe->ioprio || sqe->buf_index || sqe->splice_fd_in)) + if (unlikely(sqe->ioprio || sqe->buf_index)) return -EINVAL; if (unlikely(req->flags & REQ_F_FIXED_FILE)) return -EBADF; @@ -3836,6 +3840,16 @@ static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe req->open.filename = NULL; return ret; } + + index = READ_ONCE(sqe->file_index); + req->buf_index = index; + if (index) { + if (req->open.how.flags & O_CLOEXEC) + return -EINVAL; + if (req->buf_index != index) + return -EINVAL; + } + req->open.nofile = rlimit(RLIMIT_NOFILE); req->flags |= REQ_F_NEED_CLEANUP; return 0; @@ -3873,8 +3887,8 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags) { struct open_flags op; struct file *file; - bool nonblock_set; - bool resolve_nonblock; + bool resolve_nonblock, nonblock_set; + bool fixed = !!req->buf_index; int ret; ret = build_open_flags(&req->open.how, &op); @@ -3893,9 +3907,11 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags) op.open_flag |= O_NONBLOCK; } - ret = __get_unused_fd_flags(req->open.how.flags, req->open.nofile); - if (ret < 0) - goto err; + if (!fixed) { + ret = __get_unused_fd_flags(req->open.how.flags, req->open.nofile); + if (ret < 0) + goto err; + } file = do_filp_open(req->open.dfd, req->open.filename, &op); if (IS_ERR(file)) { @@ -3904,7 +3920,8 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags) * marginal gain for something that is now known to be a slower * path. So just put it, and we'll get a new one when we retry. */ - put_unused_fd(ret); + if (!fixed) + put_unused_fd(ret); ret = PTR_ERR(file); /* only retry if RESOLVE_CACHED wasn't already set by application */ @@ -3917,7 +3934,11 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags) if ((issue_flags & IO_URING_F_NONBLOCK) && !nonblock_set) file->f_flags &= ~O_NONBLOCK; fsnotify_open(file); - fd_install(ret, file); + + if (!fixed) + fd_install(ret, file); + else + ret = io_install_fixed_file(req, file, issue_flags); err: putname(req->open.filename); req->flags &= ~REQ_F_NEED_CLEANUP; @@ -7846,6 +7867,50 @@ static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file, #endif } +static int io_install_fixed_file(struct io_kiocb *req, struct file *file, + unsigned int issue_flags) +{ + struct io_ring_ctx *ctx = req->ctx; + int i = req->buf_index - 1; + bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK; + struct io_fixed_file *file_slot; + int ret = -EBADF; + + if (WARN_ON_ONCE(req->buf_index == 0)) + goto err; + + io_ring_submit_lock(ctx, !force_nonblock); + if (file->f_op == &io_uring_fops) + goto err; + ret = -ENXIO; + if (!ctx->file_data) + goto err; + ret = -EINVAL; + if (i >= ctx->nr_user_files) + goto err; + + i = array_index_nospec(i, ctx->nr_user_files); + file_slot = io_fixed_file_slot(&ctx->file_table, i); + ret = -EBADF; + if (file_slot->file_ptr) + goto err; + + *io_get_tag_slot(ctx->file_data, i) = 0; + io_fixed_file_set(file_slot, file); + ret = io_sqe_file_register(ctx, file, i); + if (ret) { + file_slot->file_ptr = 0; + goto err; + } + + ret = 0; +err: + io_ring_submit_unlock(ctx, !force_nonblock); + if (ret) + fput(file); + return ret; +} + static int io_queue_rsrc_removal(struct io_rsrc_data *data, unsigned idx, struct io_rsrc_node *node, void *rsrc) { @@ -10311,6 +10376,7 @@ static int __init io_uring_init(void) BUILD_BUG_SQE_ELEM(40, __u16, buf_group); BUILD_BUG_SQE_ELEM(42, __u16, personality); BUILD_BUG_SQE_ELEM(44, __s32, splice_fd_in); + BUILD_BUG_SQE_ELEM(44, __u32, file_index); BUILD_BUG_ON(sizeof(struct io_uring_files_update) != sizeof(struct io_uring_rsrc_update)); diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index 79126d5cd289..45a4f2373694 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -55,7 +55,10 @@ struct io_uring_sqe { } __attribute__((packed)); /* personality to use, if used */ __u16 personality; - __s32 splice_fd_in; + union { + __s32 splice_fd_in; + __u32 file_index; + }; __u64 __pad2[2]; };