[PATCH] dm: support ioctls on mapped devices

Extend the core device-mapper infrastructure to accept arbitrary ioctls on a
mapped device provided that it has exactly one target and it is capable of
supporting ioctls.

[We can't use unlocked_ioctl because we need 'inode': 'file' might be NULL.
Is it worth changing this?]
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Arnd Bergmann <arnd@arndb.de> wrote:

> Am Wednesday 21 June 2006 21:31 schrieb Alasdair G Kergon:
> > static struct block_device_operations dm_blk_dops = {
> > .open = dm_blk_open,
> > .release = dm_blk_close,
> > +.ioctl = dm_blk_ioctl,
> > .getgeo = dm_blk_getgeo,
> > .owner = THIS_MODULE
>
> I guess this also needs a ->compat_ioctl method, otherwise it won't
> work for ioctl numbers that have a compat_ioctl implementation in the
> low-level device driver.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/dm.c

@@ -20,6 +20,7 @@
 #include <linux/idr.h>
 #include <linux/hdreg.h>
 #include <linux/blktrace_api.h>
+#include <linux/smp_lock.h>
 
 #define DM_MSG_PREFIX "core"
 
@@ -288,6 +289,45 @@ static int dm_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
 	return dm_get_geometry(md, geo);
 }
 
+static int dm_blk_ioctl(struct inode *inode, struct file *file,
+			unsigned int cmd, unsigned long arg)
+{
+	struct mapped_device *md;
+	struct dm_table *map;
+	struct dm_target *tgt;
+	int r = -ENOTTY;
+
+	/* We don't really need this lock, but we do need 'inode'. */
+	unlock_kernel();
+
+	md = inode->i_bdev->bd_disk->private_data;
+
+	map = dm_get_table(md);
+
+	if (!map || !dm_table_get_size(map))
+		goto out;
+
+	/* We only support devices that have a single target */
+	if (dm_table_get_num_targets(map) != 1)
+		goto out;
+
+	tgt = dm_table_get_target(map, 0);
+
+	if (dm_suspended(md)) {
+		r = -EAGAIN;
+		goto out;
+	}
+
+	if (tgt->type->ioctl)
+		r = tgt->type->ioctl(tgt, inode, file, cmd, arg);
+
+out:
+	dm_table_put(map);
+
+	lock_kernel();
+	return r;
+}
+
 static inline struct dm_io *alloc_io(struct mapped_device *md)
 {
 	return mempool_alloc(md->io_pool, GFP_NOIO);
@@ -1377,6 +1417,7 @@ int dm_suspended(struct mapped_device *md)
 static struct block_device_operations dm_blk_dops = {
 	.open = dm_blk_open,
 	.release = dm_blk_close,
+	.ioctl = dm_blk_ioctl,
 	.getgeo = dm_blk_getgeo,
 	.owner = THIS_MODULE
 };

include/linux/device-mapper.h

@@ -64,6 +64,10 @@ typedef int (*dm_status_fn) (struct dm_target *ti, status_type_t status_type,
 
 typedef int (*dm_message_fn) (struct dm_target *ti, unsigned argc, char **argv);
 
+typedef int (*dm_ioctl_fn) (struct dm_target *ti, struct inode *inode,
+			    struct file *filp, unsigned int cmd,
+			    unsigned long arg);
+
 void dm_error(const char *message);
 
 /*
@@ -91,6 +95,7 @@ struct target_type {
 	dm_resume_fn resume;
 	dm_status_fn status;
 	dm_message_fn message;
+	dm_ioctl_fn ioctl;
 };
 
 struct io_restrictions {

include/linux/dm-ioctl.h

@@ -285,7 +285,7 @@ typedef char ioctl_struct[308];
 #define DM_DEV_SET_GEOMETRY	_IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
 
 #define DM_VERSION_MAJOR	4
-#define DM_VERSION_MINOR	7
+#define DM_VERSION_MINOR	8
 #define DM_VERSION_PATCHLEVEL	0
 #define DM_VERSION_EXTRA	"-ioctl (2006-06-24)"