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List:       fedora-devel-list
Subject:    Re: btrfs and default page sizes (4k vs 64k)
From:       "Tom Seewald" <tseewald () gmail ! com>
Date:       2020-09-16 18:04:53
Message-ID: 20200916180453.970.97735 () mailman01 ! iad2 ! fedoraproject ! org
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> On Tue, Sep 15, 2020 at 7:57 PM Kevin Kofler <kevin.kofler(a)chello.at&gt; wrote:
> 
> I hate to break it to you, but this problem is not just in
> filesystems, it's in basically everything in the kernel. And we've had
> variations of problems like this for years (endianness, page size,
> pointer size, single bit vs multi-bit booleans, etc.). I've personally
> been bitten by all of these issues in some way. This comes from the
> fact that there's no such thing as "internal implementation detail of
> the kernel" by design. This is the "joy" of the monorepo
> "design"
> where everything leaks into everything else.
> 
> This didn't become a serious problem until Red Hat made the
> unfortunate (though not realized at the time) mistake of switching to
> 64k pages for ARM and POWER. We got that change in Fedora for POWER
> but not ARM. It has led to all kinds of unfortunate problems that are
> gradually being worked on and fixed upstream.
> 
> Coming back to Btrfs specifically, there is work underway upstream to
> resolve this issue. My (semi-blind) estimate is that we'll see a fix
> in Linux 5.11, but Josef (cc'd to this email) may know more about it.
> 
> 
> 
> --
> 真実はいつも一つ！/ Always, there's only one truth!

Frankly I'm disappointed that the response is to deflect criticism of btrfs by \
claiming that this is an expected issue with the kernel, and then placing the blame \
on Red Hat for using a larger page size. To my knowledge page size differences aren't \
an issue on ext4 or xfs as they default to using a 4kb block size, so saying that \
"it's in basically everything in the kernel" is at best inaccurate and at worst \
intentionally misleading. _______________________________________________
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