linux-kernel - Re: [PATCH 1/2] Add partition resize function to BLKPG ioctl

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Message-ID: <20111221204641.GB27789@redhat.com>
Date:	Wed, 21 Dec 2011 15:46:41 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Phillip Susi <psusi@....rr.com>
Cc:	joe@...ches.com, kzak@...hat.com, linux-kernel@...r.kernel.org,
	jaxboe@...ionio.com
Subject: Re: [PATCH 1/2] Add partition resize function to BLKPG ioctl

On Tue, Dec 20, 2011 at 08:53:52PM -0500, Phillip Susi wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> On 12/19/2011 03:25 PM, Vivek Goyal wrote:
> > Are there any restrictions on order of partition bdev and disk bdev
> > locking.
> 
> Good point, yes, it seems you need to take the partition first.  Now that I think about it though, I don't think we need the disk mutex at all.  I thought you needed to hold it in order to iterate over the partitions, but it looks like you don't since that uses an RCU, right?
> 

I guess taking disk mutex will help us providing mutual exclusion between
multiple ioctls or multiple instances of same ioctl. Like, while you are
extending a partition and checking for overlap, you don't want another call
making progress on next partition which might overlap with this partition.

Thanks
Vivek
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