On Mon, Oct 04, 2021 at 11:32:28PM +0900, Naoya Horiguchi wrote:
> On Mon, Oct 04, 2021 at 01:55:30PM +0200, David Hildenbrand wrote:
> > On 04.10.21 13:50, Naoya Horiguchi wrote:
...
> > >
> > > Hwpoison entry for hugepage is also exposed by this patch. The below
> > > example shows how pagemap is visible in the case where a memory error
> > > hit a hugepage mapped to a process.
> > >
> > > $ ./page-types --no-summary --pid $PID --raw --list --addr 0x700000000+0x400
> > > voffset offset len flags
> > > 700000000 12fa00 1 ___U_______Ma__H_G_________________f_______1
> > > 700000001 12fa01 1ff ___________Ma___TG_________________f_______1
> > > 700000200 12f800 1 __________B________X_______________f______w_
> > > 700000201 12f801 1 ___________________X_______________f______w_ // memory failure hit this page
> > > 700000202 12f802 1fe __________B________X_______________f______w_
> > >
> > > The entries with both of "X" flag (hwpoison flag) and "w" flag (swap
> > > flag) are considered as hwpoison entries. So all pages in 2MB range
> > > are inaccessible from the process. We can get actual error location
> > > by page-types in physical address mode.
> > >
> > > $ ./page-types --no-summary --addr 0x12f800+0x200 --raw --list
> > > offset len flags
> > > 12f800 1 __________B_________________________________
> > > 12f801 1 ___________________X________________________
> > > 12f802 1fe __________B_________________________________
> > >
> > > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> > > ---
> > > fs/proc/task_mmu.c | 41 ++++++++++++++++++++++++++++++++---------
> > > include/linux/swapops.h | 13 +++++++++++++
> > > tools/vm/page-types.c | 7 ++++++-
> > > 3 files changed, 51 insertions(+), 10 deletions(-)
> >
> >
> > Please also update the documentation located at
> >
> > Documentation/admin-guide/mm/pagemap.rst
>
> I will do this in the next post.
Reading the document, I found that swap type is already exported so we
could identify hwpoison entry with it (without new PM_HWPOISON bit).
One problem is that the format of swap types (like SWP_HWPOISON) depends
on a few config macros like CONFIG_DEVICE_PRIVATE and CONFIG_MIGRATION,
so we also need to export how the swap type field is interpreted.
I thought of adding new interfaces for example under /sys/kernel/mm/swap/type_format/,
which shows info like below (assuming that all CONFIG_{DEVICE_PRIVATE,MIGRATION,MEMORY_FAILURE}
is enabled):
$ ls /sys/kernel/mm/swap/type_format/
hwpoison
migration_read
migration_write
device_write
device_read
device_exclusive_write
device_exclusive_read
$ cat /sys/kernel/mm/swap/type_format/hwpoison
25
$ cat /sys/kernel/mm/swap/type_format/device_write
28
Does it make sense or any better approach?
Thanks,
Naoya Horiguchi
