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Re: [PATCH] default to 64 bit inodes & add feature flag

To: Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: Re: [PATCH] default to 64 bit inodes & add feature flag
From: Ben Myers <bpm@xxxxxxx>
Date: Thu, 8 Mar 2012 09:37:21 -0600
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>, "Josef 'Jeff' Sipek" <jeffpc@xxxxxxxxxxxxxx>
In-reply-to: <4F5813D8.8070305@xxxxxxxxxxx>
References: <4F5798F9.2050809@xxxxxxxxxx> <20120308013413.GL3592@dastard> <4F5813D8.8070305@xxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Wed, Mar 07, 2012 at 08:05:12PM -0600, Eric Sandeen wrote:
> On 3/7/12 7:34 PM, Dave Chinner wrote:
> > On Wed, Mar 07, 2012 at 11:20:57AM -0600, Eric Sandeen wrote:
> >> From: Dave Chinner <dchinner@xxxxxxxxxx>
> >>
> >> Default to allowing 64-bit inodes on the filesystem.
> >>
> >> Add a feature bit to the the superblock to record whether 64 bit inodes 
> >> have
> >> been allocated on the filesystem or not. This allows us to reject mounting 
> >> the
> >> filesytem with inode32 if 64 bit inodes are present.
> >>
> >> Once a 64 bitinode is allocated, the inode64 superblock feature bit will 
> >> be set.
> >> Once the superblock feature bit is set, the filesystem will default to 64 
> >> bit
> >> inodes regardless of whether inode64 is specified as a mount option.
> >>
> >> To ensure only 32 bit inodes are created, the inode32 mount option must be
> >> used. If there are already 64 bit inodes as flagged by the superblock 
> >> feature
> >> bit, then the inode32 mount will be refused.
> >>
> >> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> >> ---
> >>
> >> Passing this along to revive the old discussion ... 
> > 
> > I have no objections to do this. However, the kernel patch is just
> > the tip of the iceberg when it comes to implementing this.
> > 
> > Were there patches for userspace support of the feature bit? I don't
> > recall if there were. I'm thinking that xfs_info needs to output
> > whether this is set, which means the flag needs to be added to the
> > xfs geometry ioctls in the kernel.
> 
> Nope, you just put this patch out as a suggestion, and pointed out
> that userspace needed updates too.
> 
> If people are in agreement about this then we can proceed with the rest...

Please do.  I too have been burned by mounting a filesystem with big
inos without the correct mount option.  This is a great idea.

-Ben

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