On 2023/5/20 0:17, Luck, Tony wrote:
For now, the MCE_IN_KERNEL_COPYIN flag is only set for EX_TYPE_COPY
and EX_TYPE_UACCESS when copy from user, and corrupted page is
isolated in this case, for MC-safe copy, memory_failure() is not
always called, some places, like __wp_page_copy_user, copy_subpage,
copy_user_gigantic_page and ksm_might_need_to_copy manually call
memory_failure_queue() to cope with such unhandled error pages,
recently coredump hwposion recovery support[1] is asked to do the
same thing, and there are some other already existed MC-safe copy
scenarios, eg, nvdimm, dm-writecache, dax, which has similar issue.
The best way to fix them is set MCE_IN_KERNEL_COPYIN to MCE_SAFE
exception, then kill_me_never() will be queued to call memory_failure()
in do_machine_check() to isolate corrupted page, which avoid calling
memory_failure_queue() after every MC-safe copy return.
[1] https://lkml.kernel.org/r/20230417045323.11054-1-wangkefeng.wang@xxxxxxxxxx
Is this patch in addition to, or instead of, the earlier core dump patch?
This is an addition, in previous coredump patch, manually call
memory_failure_queue()
to be asked to cope with corrupted page, and it is similar to your
"Copy-on-write poison recovery"[1], but after some discussion, I think
we could add MCE_IN_KERNEL_COPYIN to all MC-safe copy, which will
cope with corrupted page in the core do_machine_check() instead of
do it one-by-one.
The related patch is
normal page CoW [1]
huge page CoW [2]
coredump [3]
ksm might copy [4]
[1] d302c2398ba2 ("mm, hwpoison: when copy-on-write hits poison, take
page offline")
a873dfe1032a ("mm, hwpoison: try to recover from copy-on write faults")
[2] 1cb9dc4b475c ("mm: hwpoison: support recovery from HugePage
copy-on-write faults")
[3] 245f09226893 ("mm: hwpoison: coredump: support recovery from
dump_user_range()")
[4] 6b970599e807 ("mm: hwpoison: support recovery from
ksm_might_need_to_copy()")
All of them are in v6.4-rc1.
Thanks.
Kefeng
I'd like to run some tests. Can you point me a the precise set of patches
that I should apply please?
-Tony
