We normally have to fget/fput for each IO we do on a file. Even with the batching we do, the cost of the atomic inc/dec of the file usage count adds up.
This adds IORING_REGISTER_FILES, and IORING_UNREGISTER_FILES opcodes for the io_uring_register(2) system call. The arguments passed in must be an array of __s32 holding file descriptors, and nr_args should hold the number of file descriptors the application wishes to pin for the duration of the io_uring context (or until IORING_UNREGISTER_FILES is called). When used, the application must set IOSQE_FIXED_FILE in the sqe->flags member. Then, instead of setting sqe->fd to the real fd, it sets sqe->fd to the index in the array passed in to IORING_REGISTER_FILES. Files are automatically unregistered when the io_uring context is torn down. An application need only unregister if it wishes to register a few set of fds. Signed-off-by: Jens Axboe <[email protected]> --- fs/io_uring.c | 125 +++++++++++++++++++++++++++++----- include/uapi/linux/io_uring.h | 9 ++- 2 files changed, 116 insertions(+), 18 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 63ad09e7cdc7..86add82e1008 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -100,6 +100,10 @@ struct io_ring_ctx { struct fasync_struct *cq_fasync; } ____cacheline_aligned_in_smp; + /* if used, fixed file set */ + struct file **user_files; + unsigned nr_user_files; + /* if used, fixed mapped user buffers */ unsigned nr_user_bufs; struct io_mapped_ubuf *user_bufs; @@ -137,6 +141,7 @@ struct io_kiocb { #define REQ_F_FORCE_NONBLOCK 1 /* inline submission attempt */ #define REQ_F_IOPOLL_COMPLETED 2 /* polled IO has completed */ #define REQ_F_IOPOLL_EAGAIN 4 /* submission got EAGAIN */ +#define REQ_F_FIXED_FILE 8 /* ctx owns file */ u64 user_data; u64 res; @@ -359,15 +364,17 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events, * Batched puts of the same file, to avoid dirtying the * file usage count multiple times, if avoidable. */ - if (!file) { - file = req->rw.ki_filp; - file_count = 1; - } else if (file == req->rw.ki_filp) { - file_count++; - } else { - fput_many(file, file_count); - file = req->rw.ki_filp; - file_count = 1; + if (!(req->flags & REQ_F_FIXED_FILE)) { + if (!file) { + file = req->rw.ki_filp; + file_count = 1; + } else if (file == req->rw.ki_filp) { + file_count++; + } else { + fput_many(file, file_count); + file = req->rw.ki_filp; + file_count = 1; + } } if (to_free == ARRAY_SIZE(reqs)) @@ -504,13 +511,19 @@ static void kiocb_end_write(struct kiocb *kiocb) } } +static void io_fput(struct io_kiocb *req) +{ + if (!(req->flags & REQ_F_FIXED_FILE)) + fput(req->rw.ki_filp); +} + static void io_complete_rw(struct kiocb *kiocb, long res, long res2) { struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw); kiocb_end_write(kiocb); - fput(kiocb->ki_filp); + io_fput(req); io_cqring_add_event(req->ctx, req->user_data, res, 0); io_free_req(req); } @@ -614,7 +627,14 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe, struct kiocb *kiocb = &req->rw; int ret; - kiocb->ki_filp = io_file_get(state, sqe->fd); + if (sqe->flags & IOSQE_FIXED_FILE) { + if (unlikely(!ctx->user_files || sqe->fd >= ctx->nr_user_files)) + return -EBADF; + kiocb->ki_filp = ctx->user_files[sqe->fd]; + req->flags |= REQ_F_FIXED_FILE; + } else { + kiocb->ki_filp = io_file_get(state, sqe->fd); + } if (unlikely(!kiocb->ki_filp)) return -EBADF; kiocb->ki_pos = sqe->off; @@ -653,7 +673,8 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe, } return 0; out_fput: - io_file_put(state, kiocb->ki_filp); + if (!(sqe->flags & IOSQE_FIXED_FILE)) + io_file_put(state, kiocb->ki_filp); return ret; } @@ -770,7 +791,7 @@ static ssize_t io_read(struct io_kiocb *req, const struct io_uring_sqe *sqe, kfree(iovec); out_fput: if (unlikely(ret)) - fput(file); + io_fput(req); return ret; } @@ -825,7 +846,7 @@ static ssize_t io_write(struct io_kiocb *req, const struct io_uring_sqe *sqe, kfree(iovec); out_fput: if (unlikely(ret)) - fput(file); + io_fput(req); return ret; } @@ -863,14 +884,23 @@ static int io_fsync(struct io_kiocb *req, const struct io_uring_sqe *sqe, if (unlikely(sqe->fsync_flags & ~IORING_FSYNC_DATASYNC)) return -EINVAL; - file = fget(sqe->fd); + if (sqe->flags & IOSQE_FIXED_FILE) { + if (unlikely(!ctx->user_files || sqe->fd >= ctx->nr_user_files)) + return -EBADF; + file = ctx->user_files[sqe->fd]; + } else { + file = fget(sqe->fd); + } + if (unlikely(!file)) return -EBADF; ret = vfs_fsync_range(file, sqe->off, end > 0 ? end : LLONG_MAX, sqe->fsync_flags & IORING_FSYNC_DATASYNC); - fput(file); + if (!(sqe->flags & IOSQE_FIXED_FILE)) + fput(file); + io_cqring_add_event(ctx, sqe->user_data, ret, 0); io_free_req(req); return 0; @@ -988,7 +1018,7 @@ static int io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s, ssize_t ret; /* enforce forwards compatibility on users */ - if (unlikely(s->sqe->flags)) + if (unlikely(s->sqe->flags & ~IOSQE_FIXED_FILE)) return -EINVAL; req = io_get_req(ctx, state); @@ -1173,6 +1203,57 @@ static int __io_uring_enter(struct io_ring_ctx *ctx, unsigned to_submit, return ret; } +static int io_sqe_files_unregister(struct io_ring_ctx *ctx) +{ + int i; + + if (!ctx->user_files) + return -ENXIO; + + for (i = 0; i < ctx->nr_user_files; i++) + fput(ctx->user_files[i]); + + kfree(ctx->user_files); + ctx->user_files = NULL; + ctx->nr_user_files = 0; + return 0; +} + +static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg, + unsigned nr_args) +{ + __s32 __user *fds = (__s32 __user *) arg; + int fd, i, ret = 0; + + if (ctx->user_files) + return -EBUSY; + if (!nr_args) + return -EINVAL; + + ctx->user_files = kcalloc(nr_args, sizeof(struct file *), GFP_KERNEL); + if (!ctx->user_files) + return -ENOMEM; + + for (i = 0; i < nr_args; i++) { + ret = -EFAULT; + if (copy_from_user(&fd, &fds[i], sizeof(fd))) + break; + + ctx->user_files[i] = fget(fd); + + ret = -EBADF; + if (!ctx->user_files[i]) + break; + ctx->nr_user_files++; + ret = 0; + } + + if (ret) + io_sqe_files_unregister(ctx); + + return ret; +} + static int io_sq_offload_start(struct io_ring_ctx *ctx) { int ret; @@ -1468,6 +1549,7 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx) io_sq_offload_stop(ctx); io_iopoll_reap_events(ctx); io_free_scq_urings(ctx); + io_sqe_files_unregister(ctx); io_sqe_buffer_unregister(ctx); percpu_ref_exit(&ctx->refs); io_unaccount_mem(ctx, ring_pages(ctx->sq_entries, ctx->cq_entries)); @@ -1780,6 +1862,15 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, break; ret = io_sqe_buffer_unregister(ctx); break; + case IORING_REGISTER_FILES: + ret = io_sqe_files_register(ctx, arg, nr_args); + break; + case IORING_UNREGISTER_FILES: + ret = -EINVAL; + if (arg || nr_args) + break; + ret = io_sqe_files_unregister(ctx); + break; default: ret = -EINVAL; break; diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index 03ce7133c3b2..8323320077ec 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -18,7 +18,7 @@ */ struct io_uring_sqe { __u8 opcode; /* type of operation for this sqe */ - __u8 flags; /* as of now unused */ + __u8 flags; /* IOSQE_ flags */ __u16 ioprio; /* ioprio for the request */ __s32 fd; /* file descriptor to do IO on */ __u64 off; /* offset into file */ @@ -35,6 +35,11 @@ struct io_uring_sqe { }; }; +/* + * sqe->flags + */ +#define IOSQE_FIXED_FILE (1 << 0) /* use fixed fileset */ + /* * io_uring_setup() flags */ @@ -114,5 +119,7 @@ struct io_uring_params { */ #define IORING_REGISTER_BUFFERS 0 #define IORING_UNREGISTER_BUFFERS 1 +#define IORING_REGISTER_FILES 2 +#define IORING_UNREGISTER_FILES 3 #endif -- 2.17.1
