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From: Chris Mason <clm@fb.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "linux-hexagon@vger.kernel.org" <linux-hexagon@vger.kernel.org>,
	Josef Bacik <josef@toxicpanda.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	David Sterba <dsterba@suse.com>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH] btrfs: Disable BTRFS on platforms having 256K pages
Date: Thu, 10 Jun 2021 13:54:28 +0000	[thread overview]
Message-ID: <185278AF-1D87-432D-87E9-C86B3223113E@fb.com> (raw)
In-Reply-To: <a16c31f3caf448dda5d9315e056585b6fafc22c5.1623302442.git.christophe.leroy@csgroup.eu>


> On Jun 10, 2021, at 1:23 AM, Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
> 
> 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
> 
> BTRFS_MAX_COMPRESSED being 128K, BTRFS cannot support platforms with
> 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.

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

-chris


  reply	other threads:[~2021-06-10 23:46 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-10  5:23 [PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages Christophe Leroy
2021-06-10 13:54 ` Chris Mason [this message]
2021-06-10 14:50   ` [PATCH] " Christophe Leroy
2021-06-10 16:20     ` David Sterba
2021-06-11 12:58       ` Chris Mason
2021-06-11 13:21         ` David Sterba
2021-06-11 16:56           ` Chris Mason
2021-06-12 14:44     ` Brian Cain
2021-06-11 12:34 ` [PATCH] fs: " David Sterba
2021-06-11 13:47 ` Qu Wenruo
2022-01-04 23:32 ` Qu Wenruo
2022-01-06 16:31   ` Neal Gompa
2022-01-07  0:13     ` Qu Wenruo
2022-01-07  2:45       ` Hector Martin
2022-01-07  4:55       ` Michael Ellerman
2022-01-07  5:21         ` Qu Wenruo
2022-01-10  8:29   ` Christophe Leroy

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