Commit b9445598 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: openat directly into fixed fd table 



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 using normal file tables. 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: IOSQE_FIXED_FILE can't be used to switch between modes, because
accept takes a file, and it already uses the flag with a different
meaning.

Suggested-by: default avatarJosh Triplett <josh@joshtriplett.org>
Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/e9b33d1163286f51ea707f87d95bd596dada1e65.1629888991.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent d32f89da

fs/io_uring.c

+66 −8
Original line number Diff line number Diff line
@@ -580,6 +580,7 @@ struct io_sr_msg { 
struct io_open {

	struct file			*file;

	int				dfd;

	u32				file_slot;

	struct filename			*filename;

	struct open_how			how;

	unsigned long			nofile;
@@ -1063,6 +1064,9 @@ 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, u32 slot_index);



static struct kmem_cache *req_cachep;



static const struct file_operations io_uring_fops;
@@ -3864,7 +3868,7 @@ static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe 


	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;
@@ -3881,6 +3885,11 @@ static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe 
		req->open.filename = NULL;

		return ret;

	}



	req->open.file_slot = READ_ONCE(sqe->file_index);

	if (req->open.file_slot && (req->open.how.flags & O_CLOEXEC))

		return -EINVAL;



	req->open.nofile = rlimit(RLIMIT_NOFILE);

	req->flags |= REQ_F_NEED_CLEANUP;

	return 0;
@@ -3918,8 +3927,8 @@ 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->open.file_slot;

	int ret;



	ret = build_open_flags(&req->open.how, &op);
@@ -3938,9 +3947,11 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags) 
		op.open_flag |= O_NONBLOCK;

	}



	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)) {
@@ -3949,6 +3960,7 @@ 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.

		 */

		if (!fixed)

			put_unused_fd(ret);



		ret = PTR_ERR(file);
@@ -3962,7 +3974,12 @@ 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);



	if (!fixed)

		fd_install(ret, file);

	else

		ret = io_install_fixed_file(req, file, issue_flags,

					    req->open.file_slot - 1);

err:

	putname(req->open.filename);

	req->flags &= ~REQ_F_NEED_CLEANUP;
@@ -7899,6 +7916,46 @@ 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, u32 slot_index)

{

	struct io_ring_ctx *ctx = req->ctx;

	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;

	struct io_fixed_file *file_slot;

	int ret = -EBADF;



	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 (slot_index >= ctx->nr_user_files)

		goto err;



	slot_index = array_index_nospec(slot_index, ctx->nr_user_files);

	file_slot = io_fixed_file_slot(&ctx->file_table, slot_index);

	ret = -EBADF;

	if (file_slot->file_ptr)

		goto err;



	*io_get_tag_slot(ctx->file_data, slot_index) = 0;

	io_fixed_file_set(file_slot, file);

	ret = io_sqe_file_register(ctx, file, slot_index);

	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)

{
@@ -10366,6 +10423,7 @@ 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));

include/uapi/linux/io_uring.h

+4 −1
Original line number Diff line number Diff line
@@ -55,7 +55,10 @@ struct io_uring_sqe { 
	} __attribute__((packed));

	/* personality to use, if used */

	__u16	personality;

	union {

		__s32	splice_fd_in;

		__u32	file_index;

	};

	__u64	__pad2[2];

};