Re: [RFC PATCH v1 00/57] Boot-time page size selection for arm64

Petr Tesarik
2024-10-18T14:44:13Z

On Fri, 18 Oct 2024 14:56:00 +0200
Petr Tesarik <ptesarik@suse.com> wrote:

> On Thu, 17 Oct 2024 13:32:43 +0100
> Ryan Roberts <ryan.roberts@arm.com> wrote:
>
> > On 17/10/2024 13:27, Petr Tesarik wrote:
> > > On Mon, 14 Oct 2024 11:55:11 +0100
> > > Ryan Roberts <ryan.roberts@arm.com> wrote:
> > >
> > >> [...]
> > >> The series is arranged as follows:
> > >>
> > >> - patch 1: Add macros required for converting non-arch code to support
> > >> boot-time page size selection
> > >> - patches 2-36: Remove PAGE_SIZE compile-time constant assumption from all
> > >> non-arch code
> > >
> > > I have just tried to recompile the openSUSE kernel with these patches
> > > applied, and I'm running into this:
> > >
> > > CC arch/arm64/hyperv/hv_core.o
> > > In file included from ../arch/arm64/hyperv/hv_core.c:14:0:
> > > ../include/linux/hyperv.h:158:5: error: variably modified ‘reserved2’ at file scope
> > > u8 reserved2[PAGE_SIZE - 68];
> > > ^~~~~~~~~
> > >
> > > It looks like one more place which needs a patch, right?
> >
> > As mentioned in the cover letter, so far I've only converted enough to get the
> > defconfig *image* building (i.e. no modules). If you are compiling a different
> > config or compiling the modules for defconfig, you will likely run into these
> > types of issues.
> >
> > That said, I do have some patches to fix Hyper-V, which Michael Kelley was kind
> > enough to send me.
> >
> > I understand that Suse might be able to help with wider performance testing - if
> > that's the reason you are trying to compile, you could send me your config and
> > I'll start working on fixing up other drivers?
>
> You're right, performance testing is my goal.
>
> Heh, the openSUSE master config is cranked up to max. ;-) That would be
> a lot of work, and we don't need all those options for running our test
> suite. Let me disable the conflicting options instead.
>[...]
> I'll see if I can do something about btrfs. Then I can try to boot the
> kernel...

FWIW the kernel builds and _boots_ after applying this patch:

fs/btrfs/compression.h | 2 +-
fs/btrfs/defrag.c | 2 +-
fs/btrfs/extent_io.h | 2 +-
fs/btrfs/scrub.c | 2 +-
include/linux/raid/pq.h | 4 ++--
lib/raid6/algos.c | 2 +-
6 files changed, 7 insertions(+), 7 deletions(-)

--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -33,7 +33,7 @@ struct btrfs_bio;
/* Maximum length of compressed data stored on disk */
#define BTRFS_MAX_COMPRESSED (SZ_128K)
#define BTRFS_MAX_COMPRESSED_PAGES (BTRFS_MAX_COMPRESSED / PAGE_SIZE)
-static_assert((BTRFS_MAX_COMPRESSED % PAGE_SIZE) == 0);
+static_assert((BTRFS_MAX_COMPRESSED % PAGE_SIZE_MAX) == 0);

/* Maximum size of data before compression */
#define BTRFS_MAX_UNCOMPRESSED (SZ_128K)
--- a/fs/btrfs/defrag.c
+++ b/fs/btrfs/defrag.c
@@ -1144,7 +1144,7 @@ next:
}

#define CLUSTER_SIZE (SZ_256K)
-static_assert(PAGE_ALIGNED(CLUSTER_SIZE));
+static_assert(IS_ALIGNED(CLUSTER_SIZE, PAGE_SIZE_MAX));

/*
* Defrag one contiguous target range.
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -89,7 +89,7 @@ enum {
int __init extent_buffer_init_cachep(void);
void __cold extent_buffer_free_cachep(void);

-#define INLINE_EXTENT_BUFFER_PAGES (BTRFS_MAX_METADATA_BLOCKSIZE / PAGE_SIZE)
+#define INLINE_EXTENT_BUFFER_PAGES (BTRFS_MAX_METADATA_BLOCKSIZE / PAGE_SIZE_MIN)
struct extent_buffer {
u64 start;
u32 len;
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -100,7 +100,7 @@ enum scrub_stripe_flags {
SCRUB_STRIPE_FLAG_NO_REPORT,
};

-#define SCRUB_STRIPE_PAGES (BTRFS_STRIPE_LEN / PAGE_SIZE)
+#define SCRUB_STRIPE_PAGES (BTRFS_STRIPE_LEN / PAGE_SIZE_MIN)

/*
* Represent one contiguous range with a length of BTRFS_STRIPE_LEN.
--- a/include/linux/raid/pq.h
+++ b/include/linux/raid/pq.h
@@ -12,7 +12,7 @@

#include <linux/blkdev.h>

-extern const char raid6_empty_zero_page[PAGE_SIZE];
+extern const char raid6_empty_zero_page[PAGE_SIZE_MAX];

#else /* ! __KERNEL__ */
/* Used for testing in user space */
@@ -39,7 +39,7 @@ typedef uint64_t u64;
#ifndef PAGE_SHIFT
# define PAGE_SHIFT 12
#endif
-extern const char raid6_empty_zero_page[PAGE_SIZE];
+extern const char raid6_empty_zero_page[PAGE_SIZE_MAX];

#define __init
#define __exit
--- a/lib/raid6/algos.c
+++ b/lib/raid6/algos.c
@@ -19,7 +19,7 @@
#include <linux/module.h>
#include <linux/gfp.h>
/* In .bss so it's zeroed */
-const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
+const char raid6_empty_zero_page[PAGE_SIZE_MAX] __attribute__((aligned(256)));
EXPORT_SYMBOL(raid6_empty_zero_page);
#endif

Petr T