[PATCH v3 09/10] 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.

First an attempt to do a non-blocking open by handle is made. If that
fails, for example, because the target inode is not cached, a blocking
attempt is made.

Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
---
 include/uapi/linux/io_uring.h |   1 +
 io_uring/opdef.c              |  15 +++++
 io_uring/openclose.c          | 111 ++++++++++++++++++++++++++++++++++
 io_uring/openclose.h          |   8 +++
 4 files changed, 135 insertions(+)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index a4aa83ad9527..c571929e7807 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -291,6 +291,7 @@ 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 76306c9e0ecd..1aa36f3f30de 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -580,6 +580,15 @@ const struct io_issue_def io_issue_defs[] = {
 		.issue			= io_name_to_handle_at,
 #else
 		.prep			= io_eopnotsupp_prep,
+#endif
+	},
+	[IORING_OP_OPEN_BY_HANDLE_AT] = {
+#if defined(CONFIG_FHANDLE)
+		.prep			= io_open_by_handle_at_prep,
+		.issue			= io_open_by_handle_at,
+		.async_size		= sizeof(struct io_open_handle_async),
+#else
+		.prep			= io_eopnotsupp_prep,
 #endif
 	},
 };
@@ -835,6 +844,12 @@ 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",
+#if defined(CONFIG_FHANDLE)
+		.cleanup		= io_open_by_handle_cleanup,
+#endif
+	}
 };
 
 const char *io_uring_get_opcode(u8 opcode)
diff --git a/io_uring/openclose.c b/io_uring/openclose.c
index 4da2afdb9773..289d61373567 100644
--- a/io_uring/openclose.c
+++ b/io_uring/openclose.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#include <linux/exportfs.h>
 #include <linux/fs.h>
 #include <linux/file.h>
 #include <linux/fdtable.h>
@@ -245,6 +246,116 @@ int io_name_to_handle_at(struct io_kiocb *req, unsigned int issue_flags)
 	io_req_set_res(req, ret, 0);
 	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);
+	struct io_open_handle_async *ah;
+	u64 flags;
+	int ret;
+
+	flags = READ_ONCE(sqe->open_flags);
+	open->how = build_open_how(flags, 0);
+
+	ret = __io_open_prep(req, sqe);
+	if (ret)
+		return ret;
+
+	ah = io_uring_alloc_async_data(NULL, req);
+	if (!ah)
+		return -ENOMEM;
+	memset(&ah->path, 0, sizeof(ah->path));
+	ah->handle = get_user_handle(u64_to_user_ptr(READ_ONCE(sqe->addr)));
+	if (IS_ERR(ah->handle))
+		return PTR_ERR(ah->handle);
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+
+	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 io_open_handle_async *ah = req->async_data;
+	bool nonblock_set = open->how.flags & O_NONBLOCK;
+	bool fixed = !!open->file_slot;
+	struct file *file;
+	struct open_flags op;
+	int ret;
+
+	ret = build_open_flags(&open->how, &op);
+	if (ret)
+		goto err;
+
+	if (issue_flags & IO_URING_F_NONBLOCK)
+		ah->handle->handle_type |= FILEID_CACHED;
+	else
+		ah->handle->handle_type &= ~FILEID_CACHED;
+
+	if (!ah->path.dentry) {
+		/*
+		 * Handle has not yet been converted to path, either because
+		 * this is our first try, or because we tried previously with
+		 * IO_URING_F_NONBLOCK set, and failed.
+		 */
+		ret = handle_to_path(open->dfd, ah->handle, &ah->path, op.open_flag);
+		if (ret == -EAGAIN && (issue_flags & IO_URING_F_NONBLOCK))
+			return -EAGAIN;
+
+		if (ret)
+			goto err;
+	}
+
+	if (!fixed) {
+		ret = __get_unused_fd_flags(open->how.flags, open->nofile);
+		if (ret < 0)
+			goto err;
+	}
+
+	if (issue_flags & IO_URING_F_NONBLOCK) {
+		WARN_ON_ONCE(io_openat_force_async(open));
+		op.lookup_flags |= LOOKUP_CACHED;
+		op.open_flag |= O_NONBLOCK;
+	}
+	file = do_file_handle_open(&ah->path, &op);
+
+	if (IS_ERR(file)) {
+		if (!fixed)
+			put_unused_fd(ret);
+		ret = PTR_ERR(file);
+		if (ret == -EAGAIN && (issue_flags & IO_URING_F_NONBLOCK))
+			return -EAGAIN;
+		goto err;
+	}
+
+	if ((issue_flags & IO_URING_F_NONBLOCK) && !nonblock_set)
+		file->f_flags &= ~O_NONBLOCK;
+
+	if (!fixed)
+		fd_install(ret, file);
+	else
+		ret = io_fixed_fd_install(req, issue_flags, file,
+					  open->file_slot);
+
+err:
+	io_open_by_handle_cleanup(req);
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+void io_open_by_handle_cleanup(struct io_kiocb *req)
+{
+	struct io_open_handle_async *ah = req->async_data;
+
+	if (ah->path.dentry)
+		path_put(&ah->path);
+
+	kfree(ah->handle);
+}
 #endif /* CONFIG_FHANDLE */
 
 int __io_close_fixed(struct io_ring_ctx *ctx, unsigned int issue_flags,
diff --git a/io_uring/openclose.h b/io_uring/openclose.h
index 2fc1c8d35d0b..f966859a8a92 100644
--- a/io_uring/openclose.h
+++ b/io_uring/openclose.h
@@ -10,9 +10,17 @@ void io_open_cleanup(struct io_kiocb *req);
 int io_openat2_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_openat2(struct io_kiocb *req, unsigned int issue_flags);
 
+struct io_open_handle_async {
+	struct file_handle		*handle;
+	struct path			path;
+};
+
 #if defined(CONFIG_FHANDLE)
 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);
+void io_open_by_handle_cleanup(struct io_kiocb *req);
 #endif /* CONFIG_FHANDLE */
 
 int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
-- 
2.51.0