On Fri, Dec 17, 2021 at 10:27:28AM +0000, Christophe Leroy wrote:
> This is a complement of f6795053dac8 ("mm: mmap: Allow for "high"
> userspace addresses") for hugetlb.
>
> This patch adds support for "high" userspace addresses that are
> optionally supported on the system and have to be requested via a hint
> mechanism ("high" addr parameter to mmap).
>
> Architectures such as powerpc and x86 achieve this by making changes to
> their architectural versions of hugetlb_get_unmapped_area() function.
> However, arm64 uses the generic version of that function.
>
> So take into account arch_get_mmap_base() and arch_get_mmap_end() in
> hugetlb_get_unmapped_area(). To allow that, move those two macros
> out of mm/mmap.c into include/linux/sched/mm.h
>
> If these macros are not defined in architectural code then they default
> to (TASK_SIZE) and (base) so should not introduce any behavioural
> changes to architectures that do not define them.
>
> For the time being, only ARM64 is affected by this change.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> Cc: Steve Capper <steve.capper@xxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> ---
> fs/hugetlbfs/inode.c | 9 +++++----
> include/linux/sched/mm.h | 8 ++++++++
> mm/mmap.c | 8 --------
> 3 files changed, 13 insertions(+), 12 deletions(-)
This would be an ABI change but I'm fine with it. Basically with this
patch, getting hugetblfs addresses above 48-bit require explicit hint
passed to mmap().
I wonder whether we should add a fixes tag (or at least the cc stable):
Fixes: f6795053dac8 ("mm: mmap: Allow for "high" userspace addresses")
Cc: <stable@xxxxxxxxxxxxxxx> # 5.0.x
I think the original commit should have changed
hugetlb_get_unmapped_area() to have the same behaviour as
arch_get_unmapped_area(). Steve, any thoughts?
FWIW,
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
