Add a dm_ioctl_cmd to issue the equivalent of a DM ioctl call in kernel.

Signed-off-by: Enric Balletbo i Serra <enric.balle...@collabora.com>
---
 drivers/md/dm-ioctl.c         | 50 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/device-mapper.h |  6 ++++++
 2 files changed, 56 insertions(+)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index d45c681..033e31d 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -2011,3 +2011,53 @@ int dm_copy_name_and_uuid(struct mapped_device *md, char 
*name, char *uuid)
 
        return r;
 }
+
+/**
+ * dm_ioctl_cmd - Device mapper ioctl's
+ * @command: ioctl command
+ * @param: Pointer to device mapped ioctl struct
+ */
+int dm_ioctl_cmd(uint command, struct dm_ioctl *param)
+{
+       int r = 0;
+       int ioctl_flags;
+       unsigned int cmd;
+       ioctl_fn fn = NULL;
+       size_t input_param_size;
+       struct file *filp = NULL;
+
+       if (_IOC_TYPE(command) != DM_IOCTL)
+               return -ENOTTY;
+
+       /* DM_DEV_ARM_POLL is not supported */
+       if (command == DM_DEV_ARM_POLL)
+               return -EINVAL;
+
+       cmd = _IOC_NR(command);
+
+       /*
+        * Nothing more to do for the version command.
+        */
+       if (cmd == DM_VERSION_CMD)
+               return 0;
+
+       fn = lookup_ioctl(cmd, &ioctl_flags);
+       if (!fn) {
+               DMWARN("dm_ioctl: unknown command 0x%x", command);
+               return -ENOTTY;
+       }
+
+       input_param_size = param->data_size;
+       r = validate_params(cmd, param);
+       if (r)
+               return r;
+
+       param->data_size = sizeof(*param);
+       r = fn(filp, param, input_param_size);
+
+       if (unlikely(param->flags & DM_BUFFER_FULL_FLAG) &&
+           unlikely(ioctl_flags & IOCTL_FLAGS_NO_PARAMS))
+               DMERR("ioctl %d tried to output some data but has 
IOCTL_FLAGS_NO_PARAMS set", cmd);
+
+       return r;
+}
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index f4c639c..f81ba42 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -12,6 +12,7 @@
 #include <linux/blkdev.h>
 #include <linux/math64.h>
 #include <linux/ratelimit.h>
+#include <linux/dm-ioctl.h>
 
 struct dm_dev;
 struct dm_target;
@@ -446,6 +447,11 @@ int dm_noflush_suspending(struct dm_target *ti);
 void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors);
 union map_info *dm_get_rq_mapinfo(struct request *rq);
 
+/*
+ * Device mapper ioctl function.
+ */
+int dm_ioctl_cmd(unsigned int command, struct dm_ioctl *param);
+
 struct queue_limits *dm_get_queue_limits(struct mapped_device *md);
 
 /*
-- 
2.9.3

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