Re: [PATCH 1/2] io_uring: add support for truncate

[Gabriel Krisman Bertazi <krisman@suse.de>]

Tony Solomonik <tony.solomonik@gmail.com> writes:

> Libraries that are built on io_uring currently need to maintain a
> separate thread pool implementation when they want to truncate a file.

I don't think it makes sense to have both ftruncate and truncate in
io_uring.  One can just as easily link an open+ftruncate to have the
same semantics in one go.

> ---
>  include/uapi/linux/io_uring.h |  1 +
>  io_uring/Makefile             |  2 +-
>  io_uring/opdef.c              |  8 ++++++
>  io_uring/truncate.c           | 53 +++++++++++++++++++++++++++++++++++
>  io_uring/truncate.h           |  4 +++
>  5 files changed, 67 insertions(+), 1 deletion(-)
>  create mode 100644 io_uring/truncate.c
>  create mode 100644 io_uring/truncate.h
>
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index f1c16f817742..513f31ee8ce9 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -253,6 +253,7 @@ enum io_uring_op {
>  	IORING_OP_FUTEX_WAIT,
>  	IORING_OP_FUTEX_WAKE,
>  	IORING_OP_FUTEX_WAITV,
> +	IORING_OP_TRUNCATE,
>  
>  	/* this goes last, obviously */
>  	IORING_OP_LAST,
> diff --git a/io_uring/Makefile b/io_uring/Makefile
> index e5be47e4fc3b..4f8ed6530a29 100644
> --- a/io_uring/Makefile
> +++ b/io_uring/Makefile
> @@ -8,6 +8,6 @@ obj-$(CONFIG_IO_URING)		+= io_uring.o xattr.o nop.o fs.o splice.o \
>  					statx.o net.o msg_ring.o timeout.o \
>  					sqpoll.o fdinfo.o tctx.o poll.o \
>  					cancel.o kbuf.o rsrc.o rw.o opdef.o \
> -					notif.o waitid.o
> +					notif.o waitid.o truncate.o
>  obj-$(CONFIG_IO_WQ)		+= io-wq.o
>  obj-$(CONFIG_FUTEX)		+= futex.o
> diff --git a/io_uring/opdef.c b/io_uring/opdef.c
> index 799db44283c7..60827099e244 100644
> --- a/io_uring/opdef.c
> +++ b/io_uring/opdef.c
> @@ -35,6 +35,7 @@
>  #include "rw.h"
>  #include "waitid.h"
>  #include "futex.h"
> +#include "truncate.h"
>  
>  static int io_no_issue(struct io_kiocb *req, unsigned int issue_flags)
>  {
> @@ -469,6 +470,10 @@ const struct io_issue_def io_issue_defs[] = {
>  		.prep			= io_eopnotsupp_prep,
>  #endif
>  	},
> +	[IORING_OP_TRUNCATE] = {
> +		.prep			= io_truncate_prep,
> +		.issue			= io_truncate,
> +	},
>  };
>  
>  const struct io_cold_def io_cold_defs[] = {
> @@ -704,6 +709,9 @@ const struct io_cold_def io_cold_defs[] = {
>  	[IORING_OP_FUTEX_WAITV] = {
>  		.name			= "FUTEX_WAITV",
>  	},
> +	[IORING_OP_TRUNCATE] = {
> +		.name			= "TRUNCATE",
> +	},
>  };
>  
>  const char *io_uring_get_opcode(u8 opcode)
> diff --git a/io_uring/truncate.c b/io_uring/truncate.c
> new file mode 100644
> index 000000000000..82648b2fbc7e
> --- /dev/null
> +++ b/io_uring/truncate.c
> @@ -0,0 +1,53 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/fs.h>
> +#include <linux/file.h>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/syscalls.h>
> +#include <linux/io_uring.h>
> +
> +#include <uapi/linux/io_uring.h>
> +
> +#include "../fs/internal.h"
> +
> +#include "io_uring.h"
> +#include "truncate.h"
> +
> +struct io_trunc {
> +	struct files    *file;
> +	char __user     *pathname;
> +	loff_t				len;
> +};
> +
> +int io_truncate_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> +{
> +	struct io_trunc *tr = io_kiocb_to_cmd(req, struct io_trunc);
> +
> +	if (sqe->off || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in)
> +		return -EINVAL;
> +	if (unlikely(req->flags & REQ_F_FIXED_FILE))
> +		return -EBADF;
> +
> +	tr->pathname = u64_to_user_ptr(READ_ONCE(sqe->addr));
> +	tr->len = READ_ONCE(sqe->len);
> +
> +	req->flags |= REQ_F_NEED_CLEANUP;
> +	req->flags |= REQ_F_FORCE_ASYNC;
> +	return 0;
> +}
> +
> +int io_truncate(struct io_kiocb *req, unsigned int issue_flags)
> +{
> +	struct io_trunc *tr = io_kiocb_to_cmd(req, struct io_trunc);
> +	int ret;
> +
> +	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
> +
> +	ret = do_sys_truncate(tr->pathname, tr->len);
> +
> +	req->flags &= ~REQ_F_NEED_CLEANUP;
> +	io_req_set_res(req, ret, 0);
> +	return IOU_OK;
> +}
> diff --git a/io_uring/truncate.h b/io_uring/truncate.h
> new file mode 100644
> index 000000000000..ab17cb9acc90
> --- /dev/null
> +++ b/io_uring/truncate.h
> @@ -0,0 +1,4 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +int io_truncate_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
> +int io_truncate(struct io_kiocb *req, unsigned int issue_flags);

-- 
Gabriel Krisman Bertazi