-----Original Message-----
From: Christophe Leroy <redacted>

...

Le 10/06/2021 à 15:54, Chris Mason a écrit :

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On Jun 10, 2021, at 1:23 AM, Christophe Leroy

[off-list ref] wrote:

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With a config having PAGE_SIZE set to 256K, BTRFS build fails
with the following message

include/linux/compiler_types.h:326:38: error: call to

'__compiletime_assert_791' declared with attribute error: BUILD_BUG_ON
failed: (BTRFS_MAX_COMPRESSED % PAGE_SIZE) != 0

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BTRFS_MAX_COMPRESSED being 128K, BTRFS cannot support platforms

with

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256K pages at the time being.

There are two platforms that can select 256K pages:
- hexagon
- powerpc

Disable BTRFS when 256K page size is selected.

We’ll have other subpage blocksize concerns with 256K pages, but this

BTRFS_MAX_COMPRESSED #define is arbitrary.  It’s just trying to have an
upper bound on the amount of memory we’ll need to uncompress a single
page’s worth of random reads.

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We could change it to max(PAGE_SIZE, 128K) or just bump to 256K.

But if 256K is problematic in other ways, is it worth bumping
BTRFS_MAX_COMPRESSED to 256K ?

David, in below mail, said that 256K support would require deaper changes. So
disabling BTRFS
support seems the easiest solution for the time being, at least for Stable (I
forgot the Fixes: tag
and the CC: to stable).

On powerpc, 256k pages is a corner case, it requires customised binutils, so I
don't think disabling
BTRFS is a issue there. For hexagon I don't know.

Larger page sizes like this are typical for hexagon.  Disabling btrfs on hexagon seems appropriate.

-Brian