Hi Guanyou,

On Thu, Dec 4, 2025 at 11:33 PM Guanyou Chen <chenguanyou9338@gmail.com> wrote:
>
> Hi Lianbo
>
> Kernel commit 55564814a838 ("arm64/mm: Move PTE_PRESENT_INVALID
> to overlay PTE_NG"), which is contained in Linux 6.10 and
> later kernels, changed the format of swap entries on arm64.
> Without the patch, the "vtop" command cannot display swap information
>
> before:
>     crash> vtop 2000000
>     VIRTUAL     PHYSICAL
>     2000000     (not mapped)
>
>     PAGE DIRECTORY: ffffff8106356000
>        PGD: ffffff8106356000 => 800000186355003
>        PMD: ffffff8106355080 => 8000001476f5003
>        PTE: ffffff80c76f5000 => 101a62004
>
>        PTE       OFFSET: 1055330
>     vtop: cannot determine swap location
>
> without the patch:
>     crash> vtop 2000000
>     VIRTUAL     PHYSICAL
>     2000000     (not mapped)
>
>     PAGE DIRECTORY: ffffff8106356000
>        PGD: ffffff8106356000 => 800000186355003
>        PMD: ffffff8106355080 => 8000001476f5003
>        PTE: ffffff80c76f5000 => 101a62004
>
>        PTE                     SWAP                  OFFSET
>     101a62004  /first_stage_ramdisk/dev/block/zram0  1055330
>
>           VMA           START       END     FLAGS FILE
>     ffffff81a06e8b00    2000000   22000000 100073
>
>     SWAP: /first_stage_ramdisk/dev/block/zram0  OFFSET: 1055330
>
> Link: https://lore.kernel.org/r/20240503144604.151095-4-ryan.roberts@arm.com
> Signed-off-by: Guanyou.Chen <chenguanyou@xiaomi.com>
> ---
>  arm64.c  | 11 ++++++++++-
>  memory.c |  5 ++++-
>  2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/arm64.c b/arm64.c
> index 1723595..c125655 100644
> --- a/arm64.c
> +++ b/arm64.c
> @@ -712,7 +712,16 @@ arm64_init(int when)
>             }
>         }
>
> -       if (THIS_KERNEL_VERSION >= LINUX(5,19,0)) {
> +       if (THIS_KERNEL_VERSION >= LINUX(6,10,0)) {
> +           ms->__SWP_TYPE_BITS = 5;
> +           ms->__SWP_TYPE_SHIFT = 6;
> +           ms->__SWP_TYPE_MASK = ((1UL << ms->__SWP_TYPE_BITS) - 1);
> +           ms->__SWP_OFFSET_SHIFT = 12;
> +           ms->__SWP_OFFSET_BITS = 50;
> +           ms->__SWP_OFFSET_MASK = ((1UL << ms->__SWP_OFFSET_BITS) - 1);
> +           ms->PTE_PROT_NONE = 0; /* unused */
> +           ms->PTE_FILE = 0;  /* unused */
> +       } else if (THIS_KERNEL_VERSION >= LINUX(5,19,0)) {
>             ms->__SWP_TYPE_BITS = 5;
>             ms->__SWP_TYPE_SHIFT = 3;
>             ms->__SWP_TYPE_MASK = ((1UL << ms->__SWP_TYPE_BITS) - 1);
> diff --git a/memory.c b/memory.c
> index 400d31a..cbc8d2f 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -16415,6 +16415,8 @@ get_swapdev(ulong type, char *buf)
>     ulong vfsmnt;
>     char *devname;
>     char buf1[BUFSIZE];
> +   int swap_file_is_file =
> +       STREQ(MEMBER_TYPE_NAME("swap_info_struct", "swap_file"), "file");
>
>     swap_info_init();
>
> @@ -16474,7 +16476,8 @@ get_swapdev(ulong type, char *buf)
>             vfsmnt = ULONG(vt->swap_info_struct +
>                 OFFSET(swap_info_struct_swap_vfsmnt));
>                 get_pathname(swap_file, buf, BUFSIZE, 1, vfsmnt);
> -                } else if (VALID_MEMBER (swap_info_struct_old_block_size)) {
> +                } else if (VALID_MEMBER (swap_info_struct_old_block_size)
> +                   || swap_file_is_file) {

Any reason for the extra swap_file_is_file check? From the kernel
patch link you posted, only the __SWP_TYPE_XXX changes, which is
presented in (THIS_KERNEL_VERSION >= LINUX(6,10,0), but no info
related to swap_file_is_file check?

Thanks,
Tao Liu


>             devname = vfsmount_devname(file_to_vfsmnt(swap_file),
>                 buf1, BUFSIZE);
>             get_pathname(file_to_dentry(swap_file),
> --
> 2.34.1
>
> Thanks.
> Guanyou