[PATCH 1/1] dm: adds an IOCTL to work with device-filters

[Sergei Shtepa <sergei.shtepa@veeam.com>]

The four simplest IOCTL's allow to create new filters, remove them
and pass control commands specific to each target.

Signed-off-by: Sergei Shtepa <sergei.shtepa@veeam.com>
---
 drivers/md/Makefile           |  2 +-
 drivers/md/dm-ioctl.c         | 22 ++++++++++++++++++++++
 drivers/md/flt-ctl.c          | 25 +++++++++++++++++++++++++
 drivers/md/flt-ctl.h          | 10 ++++++++++
 include/uapi/linux/dm-ioctl.h | 18 ++++++++++++++++--
 5 files changed, 74 insertions(+), 3 deletions(-)
 create mode 100644 drivers/md/flt-ctl.c
 create mode 100644 drivers/md/flt-ctl.h

diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index bd5b38bee82e..1b650950adc1 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -5,7 +5,7 @@
 
 dm-mod-y	+= dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o \
 		   dm-ioctl.o dm-io.o dm-kcopyd.o dm-sysfs.o dm-stats.o \
-		   dm-rq.o dm-interposer.o
+		   dm-rq.o dm-interposer.o flt-ctl.o
 dm-multipath-y	+= dm-path-selector.o dm-mpath.o
 dm-historical-service-time-y += dm-ps-historical-service-time.o
 dm-io-affinity-y += dm-ps-io-affinity.o
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 2bcb316144a1..f5f0c9377752 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -6,6 +6,7 @@
  */
 
 #include "dm-core.h"
+#include "flt-control.h"
 
 #include <linux/module.h>
 #include <linux/vmalloc.h>
@@ -1700,6 +1701,27 @@ static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags)
 		{DM_GET_TARGET_VERSION, 0, get_target_version},
 	};
 
+	static const struct {
+		int cmd;
+		int flags;
+		ioctl_fn fn;
+	} _flt_ioctls[] = {
+		{FLT_REMOVE_ALL_CMD, IOCTL_FLAGS_NO_PARAMS | IOCTL_FLAGS_ISSUE_GLOBAL_EVENT, filter_remove_all},
+		{FLT_CREATE_CMD, IOCTL_FLAGS_NO_PARAMS | IOCTL_FLAGS_ISSUE_GLOBAL_EVENT, filter_create},
+		{FLT_REMOVE_CMD, IOCTL_FLAGS_NO_PARAMS | IOCTL_FLAGS_ISSUE_GLOBAL_EVENT, filter_remove},
+		{FLT_CONTROL_CMD, 0, filter_control},
+	};
+
+	if (cmd >= DM_FILTER_CMD) {
+		cmd -= DM_FILTER_CMD;
+
+		if (unlikely(cmd >= ARRAY_SIZE(_flt_ioctls)))
+			return NULL;
+
+		*ioctl_flags = _flt_ioctls[cmd].flags;
+		return _flt_ioctls[cmd].fn;
+	}
+
 	if (unlikely(cmd >= ARRAY_SIZE(_ioctls)))
 		return NULL;
 
diff --git a/drivers/md/flt-ctl.c b/drivers/md/flt-ctl.c
new file mode 100644
index 000000000000..aadf04be1438
--- /dev/null
+++ b/drivers/md/flt-ctl.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/dm-ioctl.h>
+
+#include "flt-ctl.h"
+
+int filter_remove_all(struct file *filp, struct dm_ioctl *param, size_t param_size)
+{
+	return 0;
+};
+int filter_create(struct file *filp, struct dm_ioctl *param, size_t param_size)
+{
+	return 0;
+};
+int filter_remove(struct file *filp, struct dm_ioctl *param, size_t param_size)
+{
+	return 0;
+};
+int filter_control(struct file *filp, struct dm_ioctl *param, size_t param_size)
+{
+	return 0;
+};
+
diff --git a/drivers/md/flt-ctl.h b/drivers/md/flt-ctl.h
new file mode 100644
index 000000000000..61a80184abae
--- /dev/null
+++ b/drivers/md/flt-ctl.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: LGPL-2.0+ WITH Linux-syscall-note */
+#ifndef FLT_CTL_H
+#define FLT_CTL_H
+
+int filter_remove_all(struct file *filp, struct dm_ioctl *param, size_t param_size);
+int filter_create(struct file *filp, struct dm_ioctl *param, size_t param_size);
+int filter_remove(struct file *filp, struct dm_ioctl *param, size_t param_size);
+int filter_control(struct file *filp, struct dm_ioctl *param, size_t param_size);
+
+#endif
diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index e942e7d7c594..012e16761ba9 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -16,6 +16,7 @@
 #define DM_MAX_TYPE_NAME 16
 #define DM_NAME_LEN 128
 #define DM_UUID_LEN 129
+#define DM_FILTER_CMD 128	/* First filters command */
 
 /*
  * A traditional ioctl interface for the device mapper.
@@ -244,6 +245,14 @@ enum {
 	DM_DEV_SET_GEOMETRY_CMD,
 	DM_DEV_ARM_POLL_CMD,
 	DM_GET_TARGET_VERSION_CMD,
+
+	/* Reserved space for additional DM ioctl */
+
+	/* Filters commands */
+	FLT_REMOVE_ALL_CMD = DM_FILTER_CMD, /* Cleanup all filters */
+	FLT_CREATE_CMD,		/* Create new filter */
+	FLT_REMOVE_CMD,		/* Remove filter */
+	FLT_CONTROL_CMD,	/* Send a filter-specific command */
 };
 
 #define DM_IOCTL 0xfd
@@ -271,10 +280,15 @@ enum {
 #define DM_TARGET_MSG	 _IOWR(DM_IOCTL, DM_TARGET_MSG_CMD, struct dm_ioctl)
 #define DM_DEV_SET_GEOMETRY	_IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
 
+#define FLT_REMOVE_ALL   _IOWR(DM_IOCTL, FLT_REMOVE_ALL_CMD, struct dm_ioctl)
+#define FLT_CREATE       _IOWR(DM_IOCTL, FLT_CREATE_CMD, struct dm_ioctl)
+#define FLT_REMOVE       _IOWR(DM_IOCTL, FLT_REMOVE_CMD, struct dm_ioctl)
+#define FLT_CONTROL      _IOWR(DM_IOCTL, FLT_CONTROL_CMD, struct dm_ioctl)
+
 #define DM_VERSION_MAJOR	4
-#define DM_VERSION_MINOR	43
+#define DM_VERSION_MINOR	44
 #define DM_VERSION_PATCHLEVEL	0
-#define DM_VERSION_EXTRA	"-ioctl (2020-10-01)"
+#define DM_VERSION_EXTRA	"-ioctl (2021-03-03)"
 
 /* Status bits */
 #define DM_READONLY_FLAG	(1 << 0) /* In/Out */
-- 
2.20.1