Re: Path Name to kdev_t

[Christoph Hellwig <hch@infradead.org>]

On Fri, Nov 15, 2002 at 04:15:36PM +0000, Joe Thornber wrote:
> On Thu, Nov 14, 2002 at 07:19:16PM +0530, chandrasekhar.nagaraj wrote:
> > Hi,
> > 
> > In one of the part of my driver module , I have a path name to a device file
> > (for eg:- /dev/hda1) .Now if I want to obtain the associated major number
> > and minor number i.e. device ID(kdev_t) of this file what would be the
> > procedure?
> 
> I think this should be standard function, I'm sure lots of people are
> duplicating this code.  For 2.4 kernels:
> 
> /*
>  * Convert a device path to a kdev_t.
>  */
> static int lookup_device(const char *path, kdev_t *dev)
> {
> 	int r;
> 	struct nameidata nd;
> 	struct inode *inode;
> 
> 	if (!path_init(path, LOOKUP_FOLLOW, &nd))
> 		return 0;

missing LOOKUP_POSITIVE

> 
> 	if ((r = path_walk(path, &nd)))
> 		goto out;
> 
> 	inode = nd.dentry->d_inode;
> 	if (!inode) {
> 		r = -ENOENT;
> 		goto out;
> 	}
> 
> 	if (!S_ISBLK(inode->i_mode)) {
> 		r = -EINVAL;
> 		goto out;
> 	}

shouldb be -ENOTBLK

new check here:

	if (nd.mnt->mnt_flags & MNT_NODEV)
		r = -EACCES;

> 
> 	*dev = inode->i_rdev;
> 
>  out:
> 	path_release(&nd);
> 	return r;

I also think that this doesn not make much sense, you really want
name to properly opened struct block_device * instead, i.e. the firsdt halve
of get_sb_bdev()