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Date: Tue, 25 May 2010 17:05:50 +0100
From: Alasdair G Kergon <agk@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Will Drewry <wad@chromium.org>, linux-kernel@vger.kernel.org,
       Al Viro <viro@zeniv.linux.org.uk>, Nick Piggin <npiggin@suse.de>,
       Tejun Heo <tj@kernel.org>, Scott James Remnant <scott@ubuntu.com>,
       Vegard Nossum <vegard.nossum@gmail.com>,
       Harald Hoyer <harald@redhat.com>,
       Christoph Lameter <cl@linux-foundation.org>, agk@redhat.com,
       snitzer@redhat.com
Subject: Re: [PATCH 2/2] init, mount: export the name_to_dev_t symbol
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On Tue, May 25, 2010 at 11:55:35AM -0400, Christoph Hellwig wrote:
> NACK.  It's really a hack for the boot code, there's no offical name to
> dev_t mapping.
> What are you trying to use it for?
 
Device-mapper contains a subset of that code, so he's proposing we
use it here:

@@ -434,17 +435,13 @@ static int __table_get_device(struct dm_
 	int r;
 	dev_t uninitialized_var(dev);
 	struct dm_dev_internal *dd;
-	unsigned int major, minor;
 
 	BUG_ON(!t);
 
-	if (sscanf(path, "%u:%u", &major, &minor) == 2) {
-		/* Extract the major/minor numbers */
-		dev = MKDEV(major, minor);
-		if (MAJOR(dev) != major || MINOR(dev) != minor)
-			return -EOVERFLOW;
-	} else {
-		/* convert the path to a device */
+	/* lookup by major:minor or registered device name */
+	dev = name_to_dev_t(path);
+	if (!dev) {
+		/* convert the path to a device by finding its inode */
 		struct block_device *bdev = lookup_bdev(path);
 
 		if (IS_ERR(bdev))

Alasdair