CHROMIUM: dm: boot time specification of dm=

This is a wrap-up of three patches pending upstream approval.
I'm bundling them because they are interdependent, and it'll be
easier to drop it on rebase later.

1. dm: allow a dm-fs-style device to be shared via dm-ioctl

Integrates feedback from Alisdair, Mike, and Kiyoshi.

Two main changes occur here:

- 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.

- dm_table_complete() was extended to handle all of the final
functional changes required for the table to be operational once
called.

2. init: boot to device-mapper targets without an initr*

Add a dm= kernel parameter modeled after the md= parameter from
do_mounts_md.  It allows for device-mapper targets to be configured at
boot time for use early in the boot process (as the root device or
otherwise).  It also replaces /dev/XXX calls with major:minor opportunistically.

The format is dm="name uuid ro,table line 1,table line 2,...".  The
parser expects the comma to be safe to use as a newline substitute but,
otherwise, uses the normal separator of space.  Some attempt has been
made to make it forgiving of additional spaces (using skip_spaces()).

A mapped device created during boot will be assigned a minor of 0 and
may be access via /dev/dm-0.

An example dm-linear root with no uuid may look like:

root=/dev/dm-0  dm="lroot none ro, 0 4096 linear /dev/ubdb 0, 4096 4096 linear /dv/ubdc 0"

Once udev is started, /dev/dm-0 will become /dev/mapper/lroot.

Older upstream threads:
http://marc.info/?l=dm-devel&m=127429492521964&w=2
http://marc.info/?l=dm-devel&m=127429499422096&w=2
http://marc.info/?l=dm-devel&m=127429493922000&w=2

Latest upstream threads:
https://patchwork.kernel.org/patch/104859/
https://patchwork.kernel.org/patch/104860/
https://patchwork.kernel.org/patch/104861/

BUG: 27175947

Signed-off-by: Will Drewry <wad@chromium.org>
Review URL: http://codereview.chromium.org/2020011
Change-Id: I92bd53432a11241228d2e5ac89a3b20d19b05a31

2 files changed, 40 insertions, 0 deletions

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 81a79b739..1debe0433 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1849,6 +1849,45 @@ void dm_interface_exit(void)
 	dm_hash_exit();
 }
 
+
+/**
+ * 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) {
+		r = -ENXIO;
+		goto out;
+	}
+
+	/* 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));
+		r = -ENXIO;
+		goto out;
+	}
+
+	r = dm_hash_insert(name, uuid, md);
+	if (r) {
+		DMERR("%s: could not bind to '%s'", dm_device_name(md), name);
+		goto out;
+	}
+
+	/* Let udev know we've changed. */
+	dm_kobject_uevent(md, KOBJ_CHANGE, dm_get_event_nr(md));
+out:
+	return r;
+}
 /**
  * dm_copy_name_and_uuid - Copy mapped device name & uuid into supplied buffers
  * @md: Pointer to mapped_device
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index bd88d3dad..64578283d 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -11,6 +11,7 @@
 #include <linux/vmalloc.h>
 #include <linux/blkdev.h>
 #include <linux/namei.h>
+#include <linux/mount.h>
 #include <linux/ctype.h>
 #include <linux/string.h>
 #include <linux/slab.h>