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

[Tony Solomonik <tony.solomonik@gmail.com>]

Libraries that are built on io_uring currently need to maintain a
separate thread pool implementation when they want to truncate a file.
---
 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);
-- 
2.34.1