linux-ext4 - Re: [PATCH 2/2] OCFS2: Allow huge (> 16 TiB) volumes to mount

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Message-ID: <20100713012506.GA30737@dastard>
Date:	Tue, 13 Jul 2010 11:25:06 +1000
From:	Dave Chinner <david@...morbit.com>
To:	"Patrick J. LoPresti" <lopresti@...il.com>
Cc:	Andreas Dilger <adilger@...ger.ca>, ocfs2-devel@....oracle.com,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] OCFS2: Allow huge (> 16 TiB) volumes to mount

On Mon, Jul 12, 2010 at 06:08:51PM -0700, Patrick J. LoPresti wrote:
> On Mon, Jul 12, 2010 at 5:21 PM, Andreas Dilger <adilger@...ger.ca> wrote:
> > On 2010-07-11, at 11:04, Patrick J. LoPresti wrote:
> > >
> >> +     /* Absolute addressability check (borrowed from ext4/super.c) */
> >> +     if ((max_block >
> >> +          (sector_t)(~0LL) >> (osb->sb->s_blocksize_bits - 9)) ||
> >> +         (max_block > (pgoff_t)(~0LL) >> (PAGE_CACHE_SHIFT -
> >> +                                          osb->sb->s_blocksize_bits))) {
> >> +             mlog(ML_ERROR, "Volume too large "
> >> +                  "to mount safely on this system");
> >> +             status = -EFBIG;
> >> +             goto out;
> >> +     }
> >
> > This hunk of code is actually in several filesystems.  It wouldn't be a bad idea to make it a library function that can be called by the filesystem to check the kernel page cache and block layer can handle these large filesystems.
> 
> True, but some of them do it differently (e.g. see the #if switch in
> xfs_sb_validate_fsb_count).  Tracking down all variants and changing
> them is a much larger task than my simple patch.

The XFS code is different to the above because there is still a 16TB
size limit on 32 bit systemsi (i.e. page cache address limits). IOWs,
you can't just remove the above 16TB check unless you (i.e. OCFS2)
handle >16TB block devices on 32 bit systems correctly...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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