[PATCH v5 0/6] io_uring/mock: add basic infra for test mock files

[PATCH v5 0/6] io_uring/mock: add basic infra for test mock files

[Pavel Begunkov]

io_uring commands provide an ioctl style interface for files to
implement file specific operations. io_uring provides many features and
advanced api to commands, and it's getting hard to test as it requires
specific files/devices.

Add basic infrastucture for creating special mock files that will be
implementing the cmd api and using various io_uring features we want to
test. It'll also be useful to test some more obscure read/write/polling
edge cases in the future, which was initially suggested by Chase.

v5: moves headers to uapi/
    taint the kernel
v4: require CAP_ADMIN and limit to KASAN builds
v3: fix memleak, + release fop callback
v2: add rw support with basic options
    implement features not as bitmask but sequence number

Pavel Begunkov (6):
  io_uring/mock: add basic infra for test mock files
  io_uring/mock: add cmd using vectored regbufs
  io_uring/mock: add sync read/write
  io_uring/mock: allow to choose FMODE_NOWAIT
  io_uring/mock: support for async read/write
  io_uring/mock: add trivial poll handler

 MAINTAINERS                             |   1 +
 include/uapi/linux/io_uring/mock_file.h |  47 +++
 init/Kconfig                            |  11 +
 io_uring/Makefile                       |   1 +
 io_uring/mock_file.c                    | 363 ++++++++++++++++++++++++
 5 files changed, 423 insertions(+)
 create mode 100644 include/uapi/linux/io_uring/mock_file.h
 create mode 100644 io_uring/mock_file.c

-- 
2.49.0

[PATCH v5 1/6] io_uring/mock: add basic infra for test mock files

[Pavel Begunkov]

io_uring commands provide an ioctl style interface for files to
implement file specific operations. io_uring provides many features and
advanced api to commands, and it's getting hard to test as it requires
specific files/devices.

Add basic infrastucture for creating special mock files that will be
implementing the cmd api and using various io_uring features we want to
test. It'll also be useful to test some more obscure read/write/polling
edge cases in the future.

Suggested-by: chase xd <sl1589472800@gmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 MAINTAINERS                             |   1 +
 include/uapi/linux/io_uring/mock_file.h |  22 ++++
 init/Kconfig                            |  11 ++
 io_uring/Makefile                       |   1 +
 io_uring/mock_file.c                    | 148 ++++++++++++++++++++++++
 5 files changed, 183 insertions(+)
 create mode 100644 include/uapi/linux/io_uring/mock_file.h
 create mode 100644 io_uring/mock_file.c

diff --git a/MAINTAINERS b/MAINTAINERS
index a92290fffa16..088348e3b3ae 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12679,6 +12679,7 @@ F:	include/linux/io_uring.h
 F:	include/linux/io_uring_types.h
 F:	include/trace/events/io_uring.h
 F:	include/uapi/linux/io_uring.h
+F:	include/uapi/linux/io_uring/
 F:	io_uring/
 
 IPMI SUBSYSTEM
diff --git a/include/uapi/linux/io_uring/mock_file.h b/include/uapi/linux/io_uring/mock_file.h
new file mode 100644
index 000000000000..a44273fd526d
--- /dev/null
+++ b/include/uapi/linux/io_uring/mock_file.h
@@ -0,0 +1,22 @@
+#ifndef LINUX_IO_URING_MOCK_FILE_H
+#define LINUX_IO_URING_MOCK_FILE_H
+
+#include <linux/types.h>
+
+struct io_uring_mock_probe {
+	__u64		features;
+	__u64		__resv[9];
+};
+
+struct io_uring_mock_create {
+	__u32		out_fd;
+	__u32		flags;
+	__u64		__resv[15];
+};
+
+enum {
+	IORING_MOCK_MGR_CMD_PROBE,
+	IORING_MOCK_MGR_CMD_CREATE,
+};
+
+#endif
diff --git a/init/Kconfig b/init/Kconfig
index af4c2f085455..c40a7c65fb4c 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1801,6 +1801,17 @@ config GCOV_PROFILE_URING
 	  the io_uring subsystem, hence this should only be enabled for
 	  specific test purposes.
 
+config IO_URING_MOCK_FILE
+	tristate "Enable io_uring mock files (Experimental)" if EXPERT
+	default n
+	depends on IO_URING
+	help
+	  Enable mock files for io_uring subststem testing. The ABI might
+	  still change, so it's still experimental and should only be enabled
+	  for specific test purposes.
+
+	  If unsure, say N.
+
 config ADVISE_SYSCALLS
 	bool "Enable madvise/fadvise syscalls" if EXPERT
 	default y
diff --git a/io_uring/Makefile b/io_uring/Makefile
index d97c6b51d584..b3f1bd492804 100644
--- a/io_uring/Makefile
+++ b/io_uring/Makefile
@@ -21,3 +21,4 @@ obj-$(CONFIG_EPOLL)		+= epoll.o
 obj-$(CONFIG_NET_RX_BUSY_POLL)	+= napi.o
 obj-$(CONFIG_NET) += net.o cmd_net.o
 obj-$(CONFIG_PROC_FS) += fdinfo.o
+obj-$(CONFIG_IO_URING_MOCK_FILE) += mock_file.o
diff --git a/io_uring/mock_file.c b/io_uring/mock_file.c
new file mode 100644
index 000000000000..3681d0b8d8de
--- /dev/null
+++ b/io_uring/mock_file.c
@@ -0,0 +1,148 @@
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/anon_inodes.h>
+
+#include <linux/io_uring/cmd.h>
+#include <linux/io_uring_types.h>
+#include <uapi/linux/io_uring/mock_file.h>
+
+static int io_mock_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
+{
+	return -ENOTSUPP;
+}
+
+static const struct file_operations io_mock_fops = {
+	.owner		= THIS_MODULE,
+	.uring_cmd	= io_mock_cmd,
+};
+
+static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flags)
+{
+	const struct io_uring_sqe *sqe = cmd->sqe;
+	struct io_uring_mock_create mc, __user *uarg;
+	struct file *file = NULL;
+	size_t uarg_size;
+	int fd, ret;
+
+	/*
+	 * It's a testing only driver that allows exercising edge cases
+	 * that wouldn't be possible to hit otherwise.
+	 */
+	add_taint(TAINT_TEST, LOCKDEP_STILL_OK);
+
+	uarg = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	uarg_size = READ_ONCE(sqe->len);
+
+	if (sqe->ioprio || sqe->__pad1 || sqe->addr3 || sqe->file_index)
+		return -EINVAL;
+	if (uarg_size != sizeof(mc))
+		return -EINVAL;
+
+	memset(&mc, 0, sizeof(mc));
+	if (copy_from_user(&mc, uarg, uarg_size))
+		return -EFAULT;
+	if (!mem_is_zero(mc.__resv, sizeof(mc.__resv)) || mc.flags)
+		return -EINVAL;
+
+	fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
+	if (fd < 0)
+		return fd;
+
+	file = anon_inode_create_getfile("[io_uring_mock]", &io_mock_fops,
+					 NULL, O_RDWR | O_CLOEXEC, NULL);
+	if (IS_ERR(file)) {
+		ret = PTR_ERR(file);
+		goto fail;
+	}
+
+	mc.out_fd = fd;
+	if (copy_to_user(uarg, &mc, uarg_size)) {
+		fput(file);
+		ret = -EFAULT;
+		goto fail;
+	}
+
+	fd_install(fd, file);
+	return 0;
+fail:
+	put_unused_fd(fd);
+	return ret;
+}
+
+static int io_probe_mock(struct io_uring_cmd *cmd)
+{
+	const struct io_uring_sqe *sqe = cmd->sqe;
+	struct io_uring_mock_probe mp, __user *uarg;
+	size_t uarg_size;
+
+	uarg = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	uarg_size = READ_ONCE(sqe->len);
+
+	if (sqe->ioprio || sqe->__pad1 || sqe->addr3 || sqe->file_index ||
+	    uarg_size != sizeof(mp))
+		return -EINVAL;
+
+	memset(&mp, 0, sizeof(mp));
+	if (copy_from_user(&mp, uarg, uarg_size))
+		return -EFAULT;
+	if (!mem_is_zero(&mp, sizeof(mp)))
+		return -EINVAL;
+
+	mp.features = 0;
+
+	if (copy_to_user(uarg, &mp, uarg_size))
+		return -EFAULT;
+	return 0;
+}
+
+static int iou_mock_mgr_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
+{
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	switch (cmd->cmd_op) {
+	case IORING_MOCK_MGR_CMD_PROBE:
+		return io_probe_mock(cmd);
+	case IORING_MOCK_MGR_CMD_CREATE:
+		return io_create_mock_file(cmd, issue_flags);
+	}
+	return -EOPNOTSUPP;
+}
+
+static const struct file_operations iou_mock_dev_fops = {
+	.owner		= THIS_MODULE,
+	.uring_cmd	= iou_mock_mgr_cmd,
+};
+
+static struct miscdevice iou_mock_miscdev = {
+	.minor			= MISC_DYNAMIC_MINOR,
+	.name			= "io_uring_mock",
+	.fops			= &iou_mock_dev_fops,
+};
+
+static int __init io_mock_init(void)
+{
+	int ret;
+
+	ret = misc_register(&iou_mock_miscdev);
+	if (ret < 0) {
+		pr_err("Could not initialize io_uring mock device\n");
+		return ret;
+	}
+	return 0;
+}
+
+static void __exit io_mock_exit(void)
+{
+	misc_deregister(&iou_mock_miscdev);
+}
+
+module_init(io_mock_init)
+module_exit(io_mock_exit)
+
+MODULE_AUTHOR("Pavel Begunkov <asml.silence@gmail.com>");
+MODULE_DESCRIPTION("io_uring mock file");
+MODULE_LICENSE("GPL");
-- 
2.49.0

[PATCH v5 2/6] io_uring/mock: add cmd using vectored regbufs

[Pavel Begunkov]

There is a command api allowing to import vectored registered buffers,
add a new mock command that uses the feature and simply copies the
specified registered buffer into user space or vice versa.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/uapi/linux/io_uring/mock_file.h | 14 +++++
 io_uring/mock_file.c                    | 70 ++++++++++++++++++++++++-
 2 files changed, 83 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/io_uring/mock_file.h b/include/uapi/linux/io_uring/mock_file.h
index a44273fd526d..73aca477d5c8 100644
--- a/include/uapi/linux/io_uring/mock_file.h
+++ b/include/uapi/linux/io_uring/mock_file.h
@@ -3,6 +3,12 @@
 
 #include <linux/types.h>
 
+enum {
+	IORING_MOCK_FEAT_CMD_COPY,
+
+	IORING_MOCK_FEAT_END,
+};
+
 struct io_uring_mock_probe {
 	__u64		features;
 	__u64		__resv[9];
@@ -19,4 +25,12 @@ enum {
 	IORING_MOCK_MGR_CMD_CREATE,
 };
 
+enum {
+	IORING_MOCK_CMD_COPY_REGBUF,
+};
+
+enum {
+	IORING_MOCK_COPY_FROM			= 1,
+};
+
 #endif
diff --git a/io_uring/mock_file.c b/io_uring/mock_file.c
index 3681d0b8d8de..8285393f4a5b 100644
--- a/io_uring/mock_file.c
+++ b/io_uring/mock_file.c
@@ -9,8 +9,76 @@
 #include <linux/io_uring_types.h>
 #include <uapi/linux/io_uring/mock_file.h>
 
+#define IO_VALID_COPY_CMD_FLAGS		IORING_MOCK_COPY_FROM
+
+static int io_copy_regbuf(struct iov_iter *reg_iter, void __user *ubuf)
+{
+	size_t ret, copied = 0;
+	size_t buflen = PAGE_SIZE;
+	void *tmp_buf;
+
+	tmp_buf = kzalloc(buflen, GFP_KERNEL);
+	if (!tmp_buf)
+		return -ENOMEM;
+
+	while (iov_iter_count(reg_iter)) {
+		size_t len = min(iov_iter_count(reg_iter), buflen);
+
+		if (iov_iter_rw(reg_iter) == ITER_SOURCE) {
+			ret = copy_from_iter(tmp_buf, len, reg_iter);
+			if (ret <= 0)
+				break;
+			if (copy_to_user(ubuf, tmp_buf, ret))
+				break;
+		} else {
+			if (copy_from_user(tmp_buf, ubuf, len))
+				break;
+			ret = copy_to_iter(tmp_buf, len, reg_iter);
+			if (ret <= 0)
+				break;
+		}
+		ubuf += ret;
+		copied += ret;
+	}
+
+	kfree(tmp_buf);
+	return copied;
+}
+
+static int io_cmd_copy_regbuf(struct io_uring_cmd *cmd, unsigned int issue_flags)
+{
+	const struct io_uring_sqe *sqe = cmd->sqe;
+	const struct iovec __user *iovec;
+	unsigned flags, iovec_len;
+	struct iov_iter iter;
+	void __user *ubuf;
+	int dir, ret;
+
+	ubuf = u64_to_user_ptr(READ_ONCE(sqe->addr3));
+	iovec = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	iovec_len = READ_ONCE(sqe->len);
+	flags = READ_ONCE(sqe->file_index);
+
+	if (unlikely(sqe->ioprio || sqe->__pad1))
+		return -EINVAL;
+	if (flags & ~IO_VALID_COPY_CMD_FLAGS)
+		return -EINVAL;
+
+	dir = (flags & IORING_MOCK_COPY_FROM) ? ITER_SOURCE : ITER_DEST;
+	ret = io_uring_cmd_import_fixed_vec(cmd, iovec, iovec_len, dir, &iter,
+					    issue_flags);
+	if (ret)
+		return ret;
+	ret = io_copy_regbuf(&iter, ubuf);
+	return ret ? ret : -EFAULT;
+}
+
 static int io_mock_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
 {
+	switch (cmd->cmd_op) {
+	case IORING_MOCK_CMD_COPY_REGBUF:
+		return io_cmd_copy_regbuf(cmd, issue_flags);
+	}
 	return -ENOTSUPP;
 }
 
@@ -91,7 +159,7 @@ static int io_probe_mock(struct io_uring_cmd *cmd)
 	if (!mem_is_zero(&mp, sizeof(mp)))
 		return -EINVAL;
 
-	mp.features = 0;
+	mp.features = IORING_MOCK_FEAT_END;
 
 	if (copy_to_user(uarg, &mp, uarg_size))
 		return -EFAULT;
-- 
2.49.0

[PATCH v5 3/6] io_uring/mock: add sync read/write

[Pavel Begunkov]

Add support for synchronous zero read/write for mock files.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/uapi/linux/io_uring/mock_file.h |  4 +-
 io_uring/mock_file.c                    | 67 +++++++++++++++++++++++--
 2 files changed, 65 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/io_uring/mock_file.h b/include/uapi/linux/io_uring/mock_file.h
index 73aca477d5c8..de27295bb365 100644
--- a/include/uapi/linux/io_uring/mock_file.h
+++ b/include/uapi/linux/io_uring/mock_file.h
@@ -5,6 +5,7 @@
 
 enum {
 	IORING_MOCK_FEAT_CMD_COPY,
+	IORING_MOCK_FEAT_RW_ZERO,
 
 	IORING_MOCK_FEAT_END,
 };
@@ -17,7 +18,8 @@ struct io_uring_mock_probe {
 struct io_uring_mock_create {
 	__u32		out_fd;
 	__u32		flags;
-	__u64		__resv[15];
+	__u64		file_size;
+	__u64		__resv[14];
 };
 
 enum {
diff --git a/io_uring/mock_file.c b/io_uring/mock_file.c
index 8285393f4a5b..90160ccb50f0 100644
--- a/io_uring/mock_file.c
+++ b/io_uring/mock_file.c
@@ -9,6 +9,10 @@
 #include <linux/io_uring_types.h>
 #include <uapi/linux/io_uring/mock_file.h>
 
+struct io_mock_file {
+	size_t size;
+};
+
 #define IO_VALID_COPY_CMD_FLAGS		IORING_MOCK_COPY_FROM
 
 static int io_copy_regbuf(struct iov_iter *reg_iter, void __user *ubuf)
@@ -82,18 +86,59 @@ static int io_mock_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
 	return -ENOTSUPP;
 }
 
+static ssize_t io_mock_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct io_mock_file *mf = iocb->ki_filp->private_data;
+	size_t len = iov_iter_count(to);
+
+	if (iocb->ki_pos + len > mf->size)
+		return -EINVAL;
+	return iov_iter_zero(len, to);
+}
+
+static ssize_t io_mock_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct io_mock_file *mf = iocb->ki_filp->private_data;
+	size_t len = iov_iter_count(from);
+
+	if (iocb->ki_pos + len > mf->size)
+		return -EINVAL;
+	iov_iter_advance(from, len);
+	return len;
+}
+
+static loff_t io_mock_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct io_mock_file *mf = file->private_data;
+
+	return fixed_size_llseek(file, offset, whence, mf->size);
+}
+
+static int io_mock_release(struct inode *inode, struct file *file)
+{
+	struct io_mock_file *mf = file->private_data;
+
+	kfree(mf);
+	return 0;
+}
+
 static const struct file_operations io_mock_fops = {
 	.owner		= THIS_MODULE,
+	.release	= io_mock_release,
 	.uring_cmd	= io_mock_cmd,
+	.read_iter	= io_mock_read_iter,
+	.write_iter	= io_mock_write_iter,
+	.llseek		= io_mock_llseek,
 };
 
 static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flags)
 {
 	const struct io_uring_sqe *sqe = cmd->sqe;
 	struct io_uring_mock_create mc, __user *uarg;
+	struct io_mock_file *mf = NULL;
 	struct file *file = NULL;
 	size_t uarg_size;
-	int fd, ret;
+	int fd = -1, ret;
 
 	/*
 	 * It's a testing only driver that allows exercising edge cases
@@ -114,18 +159,28 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 		return -EFAULT;
 	if (!mem_is_zero(mc.__resv, sizeof(mc.__resv)) || mc.flags)
 		return -EINVAL;
+	if (mc.file_size > SZ_1G)
+		return -EINVAL;
+	mf = kzalloc(sizeof(*mf), GFP_KERNEL_ACCOUNT);
+	if (!mf)
+		return -ENOMEM;
 
-	fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
+	ret = fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
 	if (fd < 0)
-		return fd;
+		goto fail;
 
+	mf->size = mc.file_size;
 	file = anon_inode_create_getfile("[io_uring_mock]", &io_mock_fops,
-					 NULL, O_RDWR | O_CLOEXEC, NULL);
+					 mf, O_RDWR | O_CLOEXEC, NULL);
 	if (IS_ERR(file)) {
 		ret = PTR_ERR(file);
 		goto fail;
 	}
 
+	file->f_mode |= FMODE_READ | FMODE_CAN_READ |
+			FMODE_WRITE | FMODE_CAN_WRITE |
+			FMODE_LSEEK;
+
 	mc.out_fd = fd;
 	if (copy_to_user(uarg, &mc, uarg_size)) {
 		fput(file);
@@ -136,7 +191,9 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 	fd_install(fd, file);
 	return 0;
 fail:
-	put_unused_fd(fd);
+	if (fd >= 0)
+		put_unused_fd(fd);
+	kfree(mf);
 	return ret;
 }
 
-- 
2.49.0

[PATCH v5 4/6] io_uring/mock: allow to choose FMODE_NOWAIT

[Pavel Begunkov]

Add an option to choose whether the file supports FMODE_NOWAIT, that
changes the execution path io_uring request takes.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/uapi/linux/io_uring/mock_file.h | 5 +++++
 io_uring/mock_file.c                    | 8 +++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/io_uring/mock_file.h b/include/uapi/linux/io_uring/mock_file.h
index de27295bb365..125949d2b5ce 100644
--- a/include/uapi/linux/io_uring/mock_file.h
+++ b/include/uapi/linux/io_uring/mock_file.h
@@ -6,6 +6,7 @@
 enum {
 	IORING_MOCK_FEAT_CMD_COPY,
 	IORING_MOCK_FEAT_RW_ZERO,
+	IORING_MOCK_FEAT_RW_NOWAIT,
 
 	IORING_MOCK_FEAT_END,
 };
@@ -15,6 +16,10 @@ struct io_uring_mock_probe {
 	__u64		__resv[9];
 };
 
+enum {
+	IORING_MOCK_CREATE_F_SUPPORT_NOWAIT			= 1,
+};
+
 struct io_uring_mock_create {
 	__u32		out_fd;
 	__u32		flags;
diff --git a/io_uring/mock_file.c b/io_uring/mock_file.c
index 90160ccb50f0..0eb1d3bd6368 100644
--- a/io_uring/mock_file.c
+++ b/io_uring/mock_file.c
@@ -131,6 +131,8 @@ static const struct file_operations io_mock_fops = {
 	.llseek		= io_mock_llseek,
 };
 
+#define IO_VALID_CREATE_FLAGS (IORING_MOCK_CREATE_F_SUPPORT_NOWAIT)
+
 static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flags)
 {
 	const struct io_uring_sqe *sqe = cmd->sqe;
@@ -157,7 +159,9 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 	memset(&mc, 0, sizeof(mc));
 	if (copy_from_user(&mc, uarg, uarg_size))
 		return -EFAULT;
-	if (!mem_is_zero(mc.__resv, sizeof(mc.__resv)) || mc.flags)
+	if (!mem_is_zero(mc.__resv, sizeof(mc.__resv)))
+		return -EINVAL;
+	if (mc.flags & ~IO_VALID_CREATE_FLAGS)
 		return -EINVAL;
 	if (mc.file_size > SZ_1G)
 		return -EINVAL;
@@ -180,6 +184,8 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 	file->f_mode |= FMODE_READ | FMODE_CAN_READ |
 			FMODE_WRITE | FMODE_CAN_WRITE |
 			FMODE_LSEEK;
+	if (mc.flags & IORING_MOCK_CREATE_F_SUPPORT_NOWAIT)
+		file->f_mode |= FMODE_NOWAIT;
 
 	mc.out_fd = fd;
 	if (copy_to_user(uarg, &mc, uarg_size)) {
-- 
2.49.0

[PATCH v5 5/6] io_uring/mock: support for async read/write

[Pavel Begunkov]

Let the user to specify a delay to read/write request. io_uring will
start a timer, return -EIOCBQUEUED and complete the request
asynchronously after the delay pass.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/uapi/linux/io_uring/mock_file.h |  4 +-
 io_uring/mock_file.c                    | 59 +++++++++++++++++++++++--
 2 files changed, 58 insertions(+), 5 deletions(-)

diff --git a/include/uapi/linux/io_uring/mock_file.h b/include/uapi/linux/io_uring/mock_file.h
index 125949d2b5ce..c8fa77e39c68 100644
--- a/include/uapi/linux/io_uring/mock_file.h
+++ b/include/uapi/linux/io_uring/mock_file.h
@@ -7,6 +7,7 @@ enum {
 	IORING_MOCK_FEAT_CMD_COPY,
 	IORING_MOCK_FEAT_RW_ZERO,
 	IORING_MOCK_FEAT_RW_NOWAIT,
+	IORING_MOCK_FEAT_RW_ASYNC,
 
 	IORING_MOCK_FEAT_END,
 };
@@ -24,7 +25,8 @@ struct io_uring_mock_create {
 	__u32		out_fd;
 	__u32		flags;
 	__u64		file_size;
-	__u64		__resv[14];
+	__u64		rw_delay_ns;
+	__u64		__resv[13];
 };
 
 enum {
diff --git a/io_uring/mock_file.c b/io_uring/mock_file.c
index 0eb1d3bd6368..ed6a5505763e 100644
--- a/io_uring/mock_file.c
+++ b/io_uring/mock_file.c
@@ -4,13 +4,22 @@
 #include <linux/miscdevice.h>
 #include <linux/module.h>
 #include <linux/anon_inodes.h>
+#include <linux/ktime.h>
+#include <linux/hrtimer.h>
 
 #include <linux/io_uring/cmd.h>
 #include <linux/io_uring_types.h>
 #include <uapi/linux/io_uring/mock_file.h>
 
+struct io_mock_iocb {
+	struct kiocb		*iocb;
+	struct hrtimer		timer;
+	int			res;
+};
+
 struct io_mock_file {
-	size_t size;
+	size_t			size;
+	u64			rw_delay_ns;
 };
 
 #define IO_VALID_COPY_CMD_FLAGS		IORING_MOCK_COPY_FROM
@@ -86,14 +95,48 @@ static int io_mock_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
 	return -ENOTSUPP;
 }
 
+static enum hrtimer_restart io_mock_rw_timer_expired(struct hrtimer *timer)
+{
+	struct io_mock_iocb *mio = container_of(timer, struct io_mock_iocb, timer);
+	struct kiocb *iocb = mio->iocb;
+
+	WRITE_ONCE(iocb->private, NULL);
+	iocb->ki_complete(iocb, mio->res);
+	kfree(mio);
+	return HRTIMER_NORESTART;
+}
+
+static ssize_t io_mock_delay_rw(struct kiocb *iocb, size_t len)
+{
+	struct io_mock_file *mf = iocb->ki_filp->private_data;
+	struct io_mock_iocb *mio;
+
+	mio = kzalloc(sizeof(*mio), GFP_KERNEL);
+	if (!mio)
+		return -ENOMEM;
+
+	mio->iocb = iocb;
+	mio->res = len;
+	hrtimer_setup(&mio->timer, io_mock_rw_timer_expired,
+		      CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	hrtimer_start(&mio->timer, ns_to_ktime(mf->rw_delay_ns),
+		      HRTIMER_MODE_REL);
+	return -EIOCBQUEUED;
+}
+
 static ssize_t io_mock_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
 	struct io_mock_file *mf = iocb->ki_filp->private_data;
 	size_t len = iov_iter_count(to);
+	size_t nr_zeroed;
 
 	if (iocb->ki_pos + len > mf->size)
 		return -EINVAL;
-	return iov_iter_zero(len, to);
+	nr_zeroed = iov_iter_zero(len, to);
+	if (!mf->rw_delay_ns || nr_zeroed != len)
+		return nr_zeroed;
+
+	return io_mock_delay_rw(iocb, len);
 }
 
 static ssize_t io_mock_write_iter(struct kiocb *iocb, struct iov_iter *from)
@@ -103,8 +146,12 @@ static ssize_t io_mock_write_iter(struct kiocb *iocb, struct iov_iter *from)
 
 	if (iocb->ki_pos + len > mf->size)
 		return -EINVAL;
-	iov_iter_advance(from, len);
-	return len;
+	if (!mf->rw_delay_ns) {
+		iov_iter_advance(from, len);
+		return len;
+	}
+
+	return io_mock_delay_rw(iocb, len);
 }
 
 static loff_t io_mock_llseek(struct file *file, loff_t offset, int whence)
@@ -165,6 +212,9 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 		return -EINVAL;
 	if (mc.file_size > SZ_1G)
 		return -EINVAL;
+	if (mc.rw_delay_ns > NSEC_PER_SEC)
+		return -EINVAL;
+
 	mf = kzalloc(sizeof(*mf), GFP_KERNEL_ACCOUNT);
 	if (!mf)
 		return -ENOMEM;
@@ -174,6 +224,7 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 		goto fail;
 
 	mf->size = mc.file_size;
+	mf->rw_delay_ns = mc.rw_delay_ns;
 	file = anon_inode_create_getfile("[io_uring_mock]", &io_mock_fops,
 					 mf, O_RDWR | O_CLOEXEC, NULL);
 	if (IS_ERR(file)) {
-- 
2.49.0

[PATCH v5 6/6] io_uring/mock: add trivial poll handler

[Pavel Begunkov]

Add a flag that enables polling on the mock file. For now it's trivially
says that there is always data available, it'll be extended in the
future.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/uapi/linux/io_uring/mock_file.h |  2 ++
 io_uring/mock_file.c                    | 37 +++++++++++++++++++++++--
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/io_uring/mock_file.h b/include/uapi/linux/io_uring/mock_file.h
index c8fa77e39c68..debeee8e4527 100644
--- a/include/uapi/linux/io_uring/mock_file.h
+++ b/include/uapi/linux/io_uring/mock_file.h
@@ -8,6 +8,7 @@ enum {
 	IORING_MOCK_FEAT_RW_ZERO,
 	IORING_MOCK_FEAT_RW_NOWAIT,
 	IORING_MOCK_FEAT_RW_ASYNC,
+	IORING_MOCK_FEAT_POLL,
 
 	IORING_MOCK_FEAT_END,
 };
@@ -19,6 +20,7 @@ struct io_uring_mock_probe {
 
 enum {
 	IORING_MOCK_CREATE_F_SUPPORT_NOWAIT			= 1,
+	IORING_MOCK_CREATE_F_POLL				= 2,
 };
 
 struct io_uring_mock_create {
diff --git a/io_uring/mock_file.c b/io_uring/mock_file.c
index ed6a5505763e..45d3735b2708 100644
--- a/io_uring/mock_file.c
+++ b/io_uring/mock_file.c
@@ -6,6 +6,7 @@
 #include <linux/anon_inodes.h>
 #include <linux/ktime.h>
 #include <linux/hrtimer.h>
+#include <linux/poll.h>
 
 #include <linux/io_uring/cmd.h>
 #include <linux/io_uring_types.h>
@@ -20,6 +21,8 @@ struct io_mock_iocb {
 struct io_mock_file {
 	size_t			size;
 	u64			rw_delay_ns;
+	bool			pollable;
+	struct wait_queue_head	poll_wq;
 };
 
 #define IO_VALID_COPY_CMD_FLAGS		IORING_MOCK_COPY_FROM
@@ -161,6 +164,18 @@ static loff_t io_mock_llseek(struct file *file, loff_t offset, int whence)
 	return fixed_size_llseek(file, offset, whence, mf->size);
 }
 
+static __poll_t io_mock_poll(struct file *file, struct poll_table_struct *pt)
+{
+	struct io_mock_file *mf = file->private_data;
+	__poll_t mask = 0;
+
+	poll_wait(file, &mf->poll_wq, pt);
+
+	mask |= EPOLLOUT | EPOLLWRNORM;
+	mask |= EPOLLIN | EPOLLRDNORM;
+	return mask;
+}
+
 static int io_mock_release(struct inode *inode, struct file *file)
 {
 	struct io_mock_file *mf = file->private_data;
@@ -178,10 +193,22 @@ static const struct file_operations io_mock_fops = {
 	.llseek		= io_mock_llseek,
 };
 
-#define IO_VALID_CREATE_FLAGS (IORING_MOCK_CREATE_F_SUPPORT_NOWAIT)
+static const struct file_operations io_mock_poll_fops = {
+	.owner		= THIS_MODULE,
+	.release	= io_mock_release,
+	.uring_cmd	= io_mock_cmd,
+	.read_iter	= io_mock_read_iter,
+	.write_iter	= io_mock_write_iter,
+	.llseek		= io_mock_llseek,
+	.poll		= io_mock_poll,
+};
+
+#define IO_VALID_CREATE_FLAGS (IORING_MOCK_CREATE_F_SUPPORT_NOWAIT | \
+				IORING_MOCK_CREATE_F_POLL)
 
 static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flags)
 {
+	const struct file_operations *fops = &io_mock_fops;
 	const struct io_uring_sqe *sqe = cmd->sqe;
 	struct io_uring_mock_create mc, __user *uarg;
 	struct io_mock_file *mf = NULL;
@@ -223,9 +250,15 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 	if (fd < 0)
 		goto fail;
 
+	init_waitqueue_head(&mf->poll_wq);
 	mf->size = mc.file_size;
 	mf->rw_delay_ns = mc.rw_delay_ns;
-	file = anon_inode_create_getfile("[io_uring_mock]", &io_mock_fops,
+	if (mc.flags & IORING_MOCK_CREATE_F_POLL) {
+		fops = &io_mock_poll_fops;
+		mf->pollable = true;
+	}
+
+	file = anon_inode_create_getfile("[io_uring_mock]", fops,
 					 mf, O_RDWR | O_CLOEXEC, NULL);
 	if (IS_ERR(file)) {
 		ret = PTR_ERR(file);
-- 
2.49.0

Re: [PATCH v5 0/6] io_uring/mock: add basic infra for test mock files

[Jens Axboe]

On Mon, 30 Jun 2025 19:16:50 +0100, Pavel Begunkov wrote:
> io_uring commands provide an ioctl style interface for files to
> implement file specific operations. io_uring provides many features and
> advanced api to commands, and it's getting hard to test as it requires
> specific files/devices.
> 
> Add basic infrastucture for creating special mock files that will be
> implementing the cmd api and using various io_uring features we want to
> test. It'll also be useful to test some more obscure read/write/polling
> edge cases in the future, which was initially suggested by Chase.
> 
> [...]

Applied, thanks!

[1/6] io_uring/mock: add basic infra for test mock files
      (no commit info)
[2/6] io_uring/mock: add cmd using vectored regbufs
      (no commit info)
[3/6] io_uring/mock: add sync read/write
      (no commit info)
[4/6] io_uring/mock: allow to choose FMODE_NOWAIT
      (no commit info)
[5/6] io_uring/mock: support for async read/write
      (no commit info)
[6/6] io_uring/mock: add trivial poll handler
      (no commit info)

Best regards,
-- 
Jens Axboe