linux-kernel - Re: [PATCH 2/2] init, mount: export the name_to_dev

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Date:	Tue, 25 May 2010 17:05:50 +0100
From:	Alasdair G Kergon <agk@...hat.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org,
	Al Viro <viro@...iv.linux.org.uk>,
	Nick Piggin <npiggin@...e.de>, Tejun Heo <tj@...nel.org>,
	Scott James Remnant <scott@...ntu.com>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Harald Hoyer <harald@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>, agk@...hat.com,
	snitzer@...hat.com
Subject: Re: [PATCH 2/2] init, mount: export the name_to_dev_t symbol

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

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