[PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[Christophe Leroy]

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.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 fs/btrfs/Kconfig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
index 68b95ad82126..520a0f6a7d9e 100644
--- a/fs/btrfs/Kconfig
+++ b/fs/btrfs/Kconfig
@@ -18,6 +18,8 @@ config BTRFS_FS
 	select RAID6_PQ
 	select XOR_BLOCKS
 	select SRCU
+	depends on !PPC_256K_PAGES	# powerpc
+	depends on !PAGE_SIZE_256KB	# hexagon
 
 	help
 	  Btrfs is a general purpose copy-on-write filesystem with extents,
-- 
2.25.0

Re: [PATCH] btrfs: Disable BTRFS on platforms having 256K pages

[Chris Mason]

> 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

Re: [PATCH] btrfs: Disable BTRFS on platforms having 256K pages

[Christophe Leroy]

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

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.


https://lkml.org/lkml/2021/6/9/978

Le 09/06/2021 à 17:22, David Sterba a écrit :
 > On Wed, Jun 09, 2021 at 04:01:20PM +0200, Christophe Leroy wrote:
 >> Le 09/06/2021 à 15:55, kernel test robot a écrit :
 >>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
 >>> head:   368094df48e680fa51cedb68537408cfa64b788e
 >>> commit: 4eeef098b43242ed145c83fba9989d586d707589 powerpc/44x: Remove STDBINUTILS kconfig option
 >>> date:   4 months ago
 >>> config: powerpc-randconfig-r012-20210609 (attached as .config)
 >>> compiler: powerpc-linux-gcc (GCC) 9.3.0
 >>
 >> That's a BTRFS issue, and not directly linked to the above mentioned commit. Before that commit the
 >> problem was already present.
 >>
 >> Problem is that with 256k PAGE_SIZE, following BUILD_BUG() pops up:
 >>
 >> BUILD_BUG_ON((BTRFS_MAX_COMPRESSED % PAGE_SIZE) != 0)
 >
 > A 256K page is a problem for btrfs, until now I was not even aware
 > there's an architecture supporting that so. That the build fails is
 > probably best thing. Maximum metadata nodesize supported is 64K and
 > having that on a 256K page would need deeper changes, no top of the
 > currently developed subpage changes (that do 4K blocks on 64K pages).
 >

Re: [PATCH] btrfs: Disable BTRFS on platforms having 256K pages

[David Sterba]

On Thu, Jun 10, 2021 at 04:50:09PM +0200, Christophe Leroy wrote:
> 
> 
> Le 10/06/2021 à 15:54, Chris Mason a écrit :
> > 
> >> 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.
> > 
> 
> 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.

That it blew up due to the max compressed size is a coincidence. We
could have explicit BUILD_BUG_ONs for page size or other constraints
derived from the page size like INLINE_EXTENT_BUFFER_PAGES.

And there's no such thing like "just bump BTRFS_MAX_COMPRESSED to 256K".
The constant is part of on-disk format for lzo and otherwise changing it
would impact performance so this would need proper evaluation.

Re: [PATCH] btrfs: Disable BTRFS on platforms having 256K pages

[Chris Mason]

> On Jun 10, 2021, at 12:20 PM, David Sterba <dsterba@suse.cz> wrote:
> 
> On Thu, Jun 10, 2021 at 04:50:09PM +0200, Christophe Leroy wrote:
>> 
>> 
>> Le 10/06/2021 à 15:54, Chris Mason a écrit :
>>> 
>>>> 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.
>>> 
>> 
>> 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.
> 
> That it blew up due to the max compressed size is a coincidence. We
> could have explicit BUILD_BUG_ONs for page size or other constraints
> derived from the page size like INLINE_EXTENT_BUFFER_PAGES.
> 

Right, the constraint is bigger and more complex than BTRFS_MAX_COMPRESSED.

> And there's no such thing like "just bump BTRFS_MAX_COMPRESSED to 256K".
> The constant is part of on-disk format for lzo and otherwise changing it
> would impact performance so this would need proper evaluation.

Sorry, how is it baked into LZO?  It definitely will have performance implications, I agree there.

-chris

Re: [PATCH] btrfs: Disable BTRFS on platforms having 256K pages

[David Sterba]

On Fri, Jun 11, 2021 at 12:58:58PM +0000, Chris Mason wrote:
> > On Jun 10, 2021, at 12:20 PM, David Sterba <dsterba@suse.cz> wrote:
> > On Thu, Jun 10, 2021 at 04:50:09PM +0200, Christophe Leroy wrote:
> >> Le 10/06/2021 à 15:54, Chris Mason a écrit :
> >>>> On Jun 10, 2021, at 1:23 AM, Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
> > And there's no such thing like "just bump BTRFS_MAX_COMPRESSED to 256K".
> > The constant is part of on-disk format for lzo and otherwise changing it
> > would impact performance so this would need proper evaluation.
> 
> Sorry, how is it baked into LZO?  It definitely will have performance implications, I agree there.

lzo_decompress_bio:

309         /*
310          * Compressed data header check.
311          *
312          * The real compressed size can't exceed the maximum extent length, and
313          * all pages should be used (whole unused page with just the segment
314          * header is not possible).  If this happens it means the compressed
315          * extent is corrupted.
316          */
317         if (tot_len > min_t(size_t, BTRFS_MAX_COMPRESSED, srclen) ||
318             tot_len < srclen - PAGE_SIZE) {
319                 ret = -EUCLEAN;
320                 goto done;
321         }

Re: [PATCH] btrfs: Disable BTRFS on platforms having 256K pages

[Chris Mason]

> On Jun 11, 2021, at 9:21 AM, David Sterba <dsterba@suse.cz> wrote:
> 
> On Fri, Jun 11, 2021 at 12:58:58PM +0000, Chris Mason wrote:
>>> On Jun 10, 2021, at 12:20 PM, David Sterba <dsterba@suse.cz> wrote:
>>> On Thu, Jun 10, 2021 at 04:50:09PM +0200, Christophe Leroy wrote:
>>>> Le 10/06/2021 à 15:54, Chris Mason a écrit :
>>>>>> On Jun 10, 2021, at 1:23 AM, Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
>>> And there's no such thing like "just bump BTRFS_MAX_COMPRESSED to 256K".
>>> The constant is part of on-disk format for lzo and otherwise changing it
>>> would impact performance so this would need proper evaluation.
>> 
>> Sorry, how is it baked into LZO?  It definitely will have performance implications, I agree there.
> 
> lzo_decompress_bio:
> 
> 309         /*
> 310          * Compressed data header check.
> 311          *
> 312          * The real compressed size can't exceed the maximum extent length, and
> 313          * all pages should be used (whole unused page with just the segment
> 314          * header is not possible).  If this happens it means the compressed
> 315          * extent is corrupted.
> 316          */
> 317         if (tot_len > min_t(size_t, BTRFS_MAX_COMPRESSED, srclen) ||
> 318             tot_len < srclen - PAGE_SIZE) {
> 319                 ret = -EUCLEAN;
> 320                 goto done;
> 321         }

Ah I see, so going back to an old LZO kernel will get upset.  Ok, fair enough.  So if we want to bump this for other reasons, we’ll need to make an LZO max size to maintain compatibility.

-chris

RE: [PATCH] btrfs: Disable BTRFS on platforms having 256K pages

[Brian Cain]

> -----Original Message-----
> From: Christophe Leroy <christophe.leroy@csgroup.eu>
...
> Le 10/06/2021 à 15:54, Chris Mason a écrit :
> >
> >> 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.
> >
> 
> 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

Re: [PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[David Sterba]

On Thu, Jun 10, 2021 at 05:23:02AM +0000, Christophe Leroy 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.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

With updated changelog added to misc-next, thanks.

Re: [PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[Qu Wenruo]

On 2021/6/10 下午1:23, Christophe Leroy 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.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>   fs/btrfs/Kconfig | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
> index 68b95ad82126..520a0f6a7d9e 100644
> --- a/fs/btrfs/Kconfig
> +++ b/fs/btrfs/Kconfig
> @@ -18,6 +18,8 @@ config BTRFS_FS
>   	select RAID6_PQ
>   	select XOR_BLOCKS
>   	select SRCU
> +	depends on !PPC_256K_PAGES	# powerpc
> +	depends on !PAGE_SIZE_256KB	# hexagon

I'm OK to disable page size other than 4K, 16K, 32K, 64K for now.

Although for other reasons.

Not only for the BUILD_BUG_ON(), but for the fact that btrfs only
support 4K, 16K, 32K, 64K sectorsize, and requires PAGE_SIZE == sectorsize.

Although we're adding subpage support, the subpage support only comes
with 4K sectorsize on 64K page size.

Until variable length version is introduced, 256K/128K page size won't
be support.

Thus I'm fine to disable BTRFS for any arch outside of the supported
page sizes for now.

Thanks,
Qu
>
>   	help
>   	  Btrfs is a general purpose copy-on-write filesystem with extents,
>

Re: [PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[Qu Wenruo]

Hi Christophe,

I'm recently enhancing the subpage support for btrfs, and my current
branch should solve the problem for btrfs to support larger page sizes.

But unfortunately my current test environment can only provide page size
with 64K or 4K, no 16K or 128K/256K support.

Mind to test my new branch on 128K page size systems?
(256K page size support is still lacking though, which will be addressed
in the future)

https://github.com/adam900710/linux/tree/metadata_subpage_switch

Thanks,
Qu

On 2021/6/10 13:23, Christophe Leroy 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.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>   fs/btrfs/Kconfig | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
> index 68b95ad82126..520a0f6a7d9e 100644
> --- a/fs/btrfs/Kconfig
> +++ b/fs/btrfs/Kconfig
> @@ -18,6 +18,8 @@ config BTRFS_FS
>   	select RAID6_PQ
>   	select XOR_BLOCKS
>   	select SRCU
> +	depends on !PPC_256K_PAGES	# powerpc
> +	depends on !PAGE_SIZE_256KB	# hexagon
>
>   	help
>   	  Btrfs is a general purpose copy-on-write filesystem with extents,

Re: [PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[Neal Gompa]

On Wed, Jan 5, 2022 at 7:05 AM Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>
> Hi Christophe,
>
> I'm recently enhancing the subpage support for btrfs, and my current
> branch should solve the problem for btrfs to support larger page sizes.
>
> But unfortunately my current test environment can only provide page size
> with 64K or 4K, no 16K or 128K/256K support.
>
> Mind to test my new branch on 128K page size systems?
> (256K page size support is still lacking though, which will be addressed
> in the future)
>
> https://github.com/adam900710/linux/tree/metadata_subpage_switch
>

The Linux Asahi folks have a 16K page environment (M1 Macs)...

Hector, could you look at it too?



-- 
真実はいつも一つ！/ Always, there's only one truth!

Re: [PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[Qu Wenruo]

On 2022/1/7 00:31, Neal Gompa wrote:
> On Wed, Jan 5, 2022 at 7:05 AM Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>>
>> Hi Christophe,
>>
>> I'm recently enhancing the subpage support for btrfs, and my current
>> branch should solve the problem for btrfs to support larger page sizes.
>>
>> But unfortunately my current test environment can only provide page size
>> with 64K or 4K, no 16K or 128K/256K support.
>>
>> Mind to test my new branch on 128K page size systems?
>> (256K page size support is still lacking though, which will be addressed
>> in the future)
>>
>> https://github.com/adam900710/linux/tree/metadata_subpage_switch
>>
>
> The Linux Asahi folks have a 16K page environment (M1 Macs)...

Su Yue kindly helped me testing 16K page size, and it's pretty OK there.

So I'm not that concerned.

It's 128K page size that I'm a little concerned, and I have not machine
supporting that large page size to do the test.

Thanks,
Qu

>
> Hector, could you look at it too?
>
>
>

Re: [PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[Hector Martin]

On 2022/01/07 9:13, Qu Wenruo wrote:
> 
> 
> On 2022/1/7 00:31, Neal Gompa wrote:
>> On Wed, Jan 5, 2022 at 7:05 AM Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>>>
>>> Hi Christophe,
>>>
>>> I'm recently enhancing the subpage support for btrfs, and my current
>>> branch should solve the problem for btrfs to support larger page sizes.
>>>
>>> But unfortunately my current test environment can only provide page size
>>> with 64K or 4K, no 16K or 128K/256K support.
>>>
>>> Mind to test my new branch on 128K page size systems?
>>> (256K page size support is still lacking though, which will be addressed
>>> in the future)
>>>
>>> https://github.com/adam900710/linux/tree/metadata_subpage_switch
>>>
>>
>> The Linux Asahi folks have a 16K page environment (M1 Macs)...
> 
> Su Yue kindly helped me testing 16K page size, and it's pretty OK there.
> 
> So I'm not that concerned.
> 
> It's 128K page size that I'm a little concerned, and I have not machine
> supporting that large page size to do the test.
> 
> Thanks,
> Qu

I'm happy to test things on 16K in the future if you need me to :-)

-- 
Hector Martin (marcan@marcan.st)
Public Key: https://mrcn.st/pub

Re: [PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[Michael Ellerman]

Qu Wenruo <quwenruo.btrfs@gmx.com> writes:
> On 2022/1/7 00:31, Neal Gompa wrote:
>> On Wed, Jan 5, 2022 at 7:05 AM Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>>>
>>> Hi Christophe,
>>>
>>> I'm recently enhancing the subpage support for btrfs, and my current
>>> branch should solve the problem for btrfs to support larger page sizes.
>>>
>>> But unfortunately my current test environment can only provide page size
>>> with 64K or 4K, no 16K or 128K/256K support.
>>>
>>> Mind to test my new branch on 128K page size systems?
>>> (256K page size support is still lacking though, which will be addressed
>>> in the future)
>>>
>>> https://github.com/adam900710/linux/tree/metadata_subpage_switch
>>>
>>
>> The Linux Asahi folks have a 16K page environment (M1 Macs)...
>
> Su Yue kindly helped me testing 16K page size, and it's pretty OK there.
>
> So I'm not that concerned.
>
> It's 128K page size that I'm a little concerned, and I have not machine
> supporting that large page size to do the test.

Did Christophe say he had a 128K system to test on?

In mainline powerpc only supports 4K/16K/64K/256K.

AFAIK there's no arch with 128K page size support, but that's only based
on some grepping, maybe it's hidden somewhere.

cheers

Re: [PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[Qu Wenruo]

On 2022/1/7 12:55, Michael Ellerman wrote:
> Qu Wenruo <quwenruo.btrfs@gmx.com> writes:
>> On 2022/1/7 00:31, Neal Gompa wrote:
>>> On Wed, Jan 5, 2022 at 7:05 AM Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>>>>
>>>> Hi Christophe,
>>>>
>>>> I'm recently enhancing the subpage support for btrfs, and my current
>>>> branch should solve the problem for btrfs to support larger page sizes.
>>>>
>>>> But unfortunately my current test environment can only provide page size
>>>> with 64K or 4K, no 16K or 128K/256K support.
>>>>
>>>> Mind to test my new branch on 128K page size systems?
>>>> (256K page size support is still lacking though, which will be addressed
>>>> in the future)
>>>>
>>>> https://github.com/adam900710/linux/tree/metadata_subpage_switch
>>>>
>>>
>>> The Linux Asahi folks have a 16K page environment (M1 Macs)...
>>
>> Su Yue kindly helped me testing 16K page size, and it's pretty OK there.
>>
>> So I'm not that concerned.
>>
>> It's 128K page size that I'm a little concerned, and I have not machine
>> supporting that large page size to do the test.
> 
> Did Christophe say he had a 128K system to test on?
> 
> In mainline powerpc only supports 4K/16K/64K/256K.
> 
> AFAIK there's no arch with 128K page size support, but that's only based
> on some grepping, maybe it's hidden somewhere.

My bad, I thought there would be 128K since there is 256K and 64K 
support, but that's totally wrong.

I'll get PPC guys informed when the 256K page size problem is solved, 
and then ask for your help.

Thanks,
Qu

> 
> cheers
> 

Re: [PATCH] fs: btrfs: Disable BTRFS on platforms having 256K pages

[Christophe Leroy]

Hi Qu,

Le 05/01/2022 à 00:32, Qu Wenruo a écrit :
> Hi Christophe,
> 
> I'm recently enhancing the subpage support for btrfs, and my current
> branch should solve the problem for btrfs to support larger page sizes.
> 
> But unfortunately my current test environment can only provide page size
> with 64K or 4K, no 16K or 128K/256K support.
> 
> Mind to test my new branch on 128K page size systems?
> (256K page size support is still lacking though, which will be addressed
> in the future)


I don't have any system with disk, I only use flashdisks with UBIFS 
filesystem.

The reason why I did this commit was because of a build failure reported 
by Kernel Build Robot, that's it.

Also note that powerpc doesn't have 128K pages. Only 4/16/64/256.

And for 256 it requires a special version of ld and binutils that I 
don't have.

I have a board where I can do 16k pages, but again that board has no disk.

Christophe

> 
> https://github.com/adam900710/linux/tree/metadata_subpage_switch
> 
> Thanks,
> Qu
> 
> On 2021/6/10 13:23, Christophe Leroy 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.
>>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   fs/btrfs/Kconfig | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
>> index 68b95ad82126..520a0f6a7d9e 100644
>> --- a/fs/btrfs/Kconfig
>> +++ b/fs/btrfs/Kconfig
>> @@ -18,6 +18,8 @@ config BTRFS_FS
>>       select RAID6_PQ
>>       select XOR_BLOCKS
>>       select SRCU
>> +    depends on !PPC_256K_PAGES    # powerpc
>> +    depends on !PAGE_SIZE_256KB    # hexagon
>>
>>       help
>>         Btrfs is a general purpose copy-on-write filesystem with extents,