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Subject[PATCH v6 2/3] dm: export a table+mapped device to the ioctl interface
Date
From: Will Drewry <wad@chromium.org>

One function is added which allows for a programmatically created
mapped device to be inserted into the dm-ioctl hash table. This binds
the device to a name and, optional, uuid which is needed by udev and
allows for userspace management of the mapped device.

Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---
v6: none
v5: resurrection
v4: https://patchwork.kernel.org/patch/104860/
---
drivers/md/dm-ioctl.c | 36 ++++++++++++++++++++++++++++++++++++
include/linux/device-mapper.h | 6 ++++++
2 files changed, 42 insertions(+)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 4951bf9..f4c610f 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1924,6 +1924,42 @@ void dm_interface_exit(void)
}

/**
+ * dm_ioctl_export - Permanently export a mapped device via the ioctl interface
+ * @md: Pointer to mapped_device
+ * @name: Buffer (size DM_NAME_LEN) for name
+ * @uuid: Buffer (size DM_UUID_LEN) for uuid or NULL if not desired
+ */
+int dm_ioctl_export(struct mapped_device *md, const char *name,
+ const char *uuid)
+{
+ int r = 0;
+ struct hash_cell *hc;
+
+ if (!md)
+ return -ENXIO;
+
+ /* The name and uuid can only be set once. */
+ mutex_lock(&dm_hash_cells_mutex);
+ hc = dm_get_mdptr(md);
+ mutex_unlock(&dm_hash_cells_mutex);
+ if (hc) {
+ DMERR("%s: already exported", dm_device_name(md));
+ return -ENXIO;
+ }
+
+ r = dm_hash_insert(name, uuid, md);
+ if (r) {
+ DMERR("%s: could not bind to '%s'", dm_device_name(md), name);
+ return r;
+ }
+
+ /* Let udev know we've changed. */
+ dm_kobject_uevent(md, KOBJ_CHANGE, dm_get_event_nr(md));
+
+ return r;
+}
+
+/**
* dm_copy_name_and_uuid - Copy mapped device name & uuid into supplied buffers
* @md: Pointer to mapped_device
* @name: Buffer (size DM_NAME_LEN) for name
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 9f70b21..2efac3b 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -412,6 +412,12 @@ void dm_set_mdptr(struct mapped_device *md, void *ptr);
void *dm_get_mdptr(struct mapped_device *md);

/*
+ * Export the device via the ioctl interface (uses mdptr).
+ */
+int dm_ioctl_export(struct mapped_device *md, const char *name,
+ const char *uuid);
+
+/*
* A device can still be used while suspended, but I/O is deferred.
*/
int dm_suspend(struct mapped_device *md, unsigned suspend_flags);
--
2.9.3
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