On Tue, Sep 3, 2024 at 4:23 PM Anthony Yznaga <anthony.yznaga@xxxxxxxxxx> wrote:
>
> From: Khalid Aziz <khalid@xxxxxxxxxx>
>
> Add a bit to vm_flags to indicate a vma shares PTEs with others. Add
> a function to determine if a vma shares PTEs by checking this flag.
> This is to be used to find the shared page table entries on page fault
> for vmas sharing PTEs.
>
> Signed-off-by: Khalid Aziz <khalid@xxxxxxxxxx>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Signed-off-by: Anthony Yznaga <anthony.yznaga@xxxxxxxxxx>
> ---
> include/linux/mm.h | 7 +++++++
> include/trace/events/mmflags.h | 3 +++
> mm/internal.h | 5 +++++
> 3 files changed, 15 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 6549d0979b28..3aa0b3322284 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -413,6 +413,13 @@ extern unsigned int kobjsize(const void *objp);
> #define VM_DROPPABLE VM_NONE
> #endif
>
> +#ifdef CONFIG_64BIT
> +#define VM_SHARED_PT_BIT 41
> +#define VM_SHARED_PT BIT(VM_SHARED_PT_BIT)
> +#else
> +#define VM_SHARED_PT VM_NONE
> +#endif
> +
> #ifdef CONFIG_64BIT
> /* VM is sealed, in vm_flags */
> #define VM_SEALED _BITUL(63)
> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
> index b63d211bd141..e1ae1e60d086 100644
> --- a/include/trace/events/mmflags.h
> +++ b/include/trace/events/mmflags.h
> @@ -167,8 +167,10 @@ IF_HAVE_PG_ARCH_X(arch_3)
>
> #ifdef CONFIG_64BIT
> # define IF_HAVE_VM_DROPPABLE(flag, name) {flag, name},
> +# define IF_HAVE_VM_SHARED_PT(flag, name) {flag, name},
> #else
> # define IF_HAVE_VM_DROPPABLE(flag, name)
> +# define IF_HAVE_VM_SHARED_PT(flag, name)
> #endif
>
> #define __def_vmaflag_names \
> @@ -204,6 +206,7 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY, "softdirty" ) \
> {VM_HUGEPAGE, "hugepage" }, \
> {VM_NOHUGEPAGE, "nohugepage" }, \
> IF_HAVE_VM_DROPPABLE(VM_DROPPABLE, "droppable" ) \
> +IF_HAVE_VM_SHARED_PT(VM_SHARED_PT, "sharedpt" ) \
> {VM_MERGEABLE, "mergeable" } \
>
> #define show_vma_flags(flags) \
> diff --git a/mm/internal.h b/mm/internal.h
> index b4d86436565b..8005d5956b6e 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -1578,4 +1578,9 @@ void unlink_file_vma_batch_init(struct unlink_vma_file_batch *);
> void unlink_file_vma_batch_add(struct unlink_vma_file_batch *, struct vm_area_struct *);
> void unlink_file_vma_batch_final(struct unlink_vma_file_batch *);
>
Hi Anthony,
I'm really excited to see this series on the mailing list again! :) I
won't have time to review this series in too much detail, but I hope
something like it gets merged eventually.
> +static inline bool vma_is_shared(const struct vm_area_struct *vma)
> +{
> + return VM_SHARED_PT && (vma->vm_flags & VM_SHARED_PT);
> +}
Tiny comment - I find vma_is_shared() to be a bit of a confusing name,
especially given how vma_is_shared_maywrite() is defined. (Sorry if
this has already been discussed before.)
How about vma_is_shared_pt()?
