[PATCH 6/6] io_uring: add support for IORING_OP_OPEN_BY_HANDLE_AT

[Thomas Bertschinger <tahbertschinger@gmail.com>]

This adds support for open_by_handle_at(2) to io_uring.

Non-blocking open by handle is not yet supported, so this always runs in
async context.

Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
---
 include/uapi/linux/io_uring.h |  1 +
 io_uring/opdef.c              |  7 ++++
 io_uring/openclose.c          | 64 ++++++++++++++++++++++++++++++++++-
 io_uring/openclose.h          |  2 ++
 4 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 596bae788b48..946da13e1454 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -290,6 +290,7 @@ enum io_uring_op {
 	IORING_OP_WRITEV_FIXED,
 	IORING_OP_PIPE,
 	IORING_OP_NAME_TO_HANDLE_AT,
+	IORING_OP_OPEN_BY_HANDLE_AT,
 
 	/* this goes last, obviously */
 	IORING_OP_LAST,
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index ff2672bbd583..e2e0f4ed0d9d 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -578,6 +578,10 @@ const struct io_issue_def io_issue_defs[] = {
 		.prep			= io_name_to_handle_at_prep,
 		.issue			= io_name_to_handle_at,
 	},
+	[IORING_OP_OPEN_BY_HANDLE_AT] = {
+		.prep			= io_open_by_handle_at_prep,
+		.issue			= io_open_by_handle_at,
+	},
 };
 
 const struct io_cold_def io_cold_defs[] = {
@@ -831,6 +835,9 @@ const struct io_cold_def io_cold_defs[] = {
 	[IORING_OP_NAME_TO_HANDLE_AT] = {
 		.name			= "NAME_TO_HANDLE_AT",
 	},
+	[IORING_OP_OPEN_BY_HANDLE_AT] = {
+		.name			= "OPEN_BY_HANDLE_AT",
+	}
 };
 
 const char *io_uring_get_opcode(u8 opcode)
diff --git a/io_uring/openclose.c b/io_uring/openclose.c
index 8be061783207..5be17d7a46e0 100644
--- a/io_uring/openclose.c
+++ b/io_uring/openclose.c
@@ -22,7 +22,13 @@ struct io_open {
 	struct file			*file;
 	int				dfd;
 	u32				file_slot;
-	struct filename			*filename;
+	union {
+		/* For openat(), openat2() */
+		struct filename		*filename;
+
+		/* For open_by_handle_at() */
+		struct file_handle __user *ufh;
+	};
 	struct open_how			how;
 	unsigned long			nofile;
 };
@@ -244,6 +250,62 @@ int io_name_to_handle_at(struct io_kiocb *req, unsigned int issue_flags)
 	return IOU_COMPLETE;
 }
 
+int io_open_by_handle_at_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_open *open = io_kiocb_to_cmd(req, struct io_open);
+	u64 flags;
+
+	flags = READ_ONCE(sqe->open_flags);
+	open->how = build_open_how(flags, 0);
+	open->ufh = u64_to_user_ptr(READ_ONCE(sqe->addr));
+
+	__io_open_prep(req, sqe);
+
+	return 0;
+}
+
+int io_open_by_handle_at(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_open *open = io_kiocb_to_cmd(req, struct io_open);
+	struct file *file;
+	bool fixed = !!open->file_slot;
+	int ret;
+
+	/*
+	 * Always try again if we aren't supposed to block, because there is no
+	 * way of preventing the FS implementation from blocking.
+	 */
+	if (issue_flags & IO_URING_F_NONBLOCK)
+		return -EAGAIN;
+
+	if (!fixed) {
+		ret = __get_unused_fd_flags(open->how.flags, open->nofile);
+		if (ret < 0)
+			goto err;
+	}
+
+	file = __do_handle_open(open->dfd, open->ufh, open->how.flags);
+
+	if (IS_ERR(file)) {
+		if (!fixed)
+			put_unused_fd(ret);
+		ret = PTR_ERR(file);
+		goto err;
+	}
+
+	if (!fixed)
+		fd_install(ret, file);
+	else
+		ret = io_fixed_fd_install(req, issue_flags, file,
+					  open->file_slot);
+
+err:
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
 int __io_close_fixed(struct io_ring_ctx *ctx, unsigned int issue_flags,
 		     unsigned int offset)
 {
diff --git a/io_uring/openclose.h b/io_uring/openclose.h
index 3d1096abffac..a6304fa856bf 100644
--- a/io_uring/openclose.h
+++ b/io_uring/openclose.h
@@ -12,6 +12,8 @@ int io_openat2(struct io_kiocb *req, unsigned int issue_flags);
 
 int io_name_to_handle_at_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_name_to_handle_at(struct io_kiocb *req, unsigned int issue_flags);
+int io_open_by_handle_at_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_open_by_handle_at(struct io_kiocb *req, unsigned int issue_flags);
 
 int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_close(struct io_kiocb *req, unsigned int issue_flags);
-- 
2.50.1