Commit 1339f24b authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring: allow allocated fixed files for openat/openat2 



If the application passes in IORING_FILE_INDEX_ALLOC as the file_slot,
then that's a hint to allocate a fixed file descriptor rather than have
one be passed in directly.

This can be useful for having io_uring manage the direct descriptor space.

Normal open direct requests will complete with 0 for success, and < 0
in case of error. If io_uring is asked to allocated the direct descriptor,
then the direct descriptor is returned in case of success.

Reviewed-by: default avatarHao Xu <howeyxu@tencent.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b70b8e33

fs/io_uring.c

+33 −3
Original line number Diff line number Diff line
@@ -4697,7 +4697,7 @@ static int io_openat2_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) 
	return __io_openat_prep(req, sqe);

}



static int __maybe_unused io_file_bitmap_get(struct io_ring_ctx *ctx)

static int io_file_bitmap_get(struct io_ring_ctx *ctx)

{

	struct io_file_table *table = &ctx->file_table;

	unsigned long nr = ctx->nr_user_files;
@@ -4722,6 +4722,36 @@ static int __maybe_unused io_file_bitmap_get(struct io_ring_ctx *ctx) 
	return -ENFILE;

}



static int io_fixed_fd_install(struct io_kiocb *req, unsigned int issue_flags,

			       struct file *file, unsigned int file_slot)

{

	bool alloc_slot = file_slot == IORING_FILE_INDEX_ALLOC;

	struct io_ring_ctx *ctx = req->ctx;

	int ret;



	if (alloc_slot) {

		io_ring_submit_lock(ctx, issue_flags);

		ret = io_file_bitmap_get(ctx);

		if (unlikely(ret < 0)) {

			io_ring_submit_unlock(ctx, issue_flags);

			return ret;

		}



		file_slot = ret;

	} else {

		file_slot--;

	}



	ret = io_install_fixed_file(req, file, issue_flags, file_slot);

	if (alloc_slot) {

		io_ring_submit_unlock(ctx, issue_flags);

		if (!ret)

			return file_slot;

	}



	return ret;

}



static int io_openat2(struct io_kiocb *req, unsigned int issue_flags)

{

	struct open_flags op;
@@ -4777,8 +4807,8 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags) 
	if (!fixed)

		fd_install(ret, file);

	else

		ret = io_install_fixed_file(req, file, issue_flags,

					    req->open.file_slot - 1);

		ret = io_fixed_fd_install(req, issue_flags, file,

						req->open.file_slot);

err:

	putname(req->open.filename);

	req->flags &= ~REQ_F_NEED_CLEANUP;

include/uapi/linux/io_uring.h

+9 −0
Original line number Diff line number Diff line
@@ -63,6 +63,15 @@ struct io_uring_sqe { 
	__u64	__pad2[2];

};



/*

 * If sqe->file_index is set to this for opcodes that instantiate a new

 * direct descriptor (like openat/openat2/accept), then io_uring will allocate

 * an available direct descriptor instead of having the application pass one

 * in. The picked direct descriptor will be returned in cqe->res, or -ENFILE

 * if the space is full.

 */

#define IORING_FILE_INDEX_ALLOC		(~0U)



enum {

	IOSQE_FIXED_FILE_BIT,

	IOSQE_IO_DRAIN_BIT,