Messages in this thread | | | Date | Wed, 12 Apr 2023 11:13:50 -0700 | From | Mike Kravetz <> | Subject | Re: [PATCH -next] mm: hwpoison: support recovery from HugePage copy-on-write faults |
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On 04/11/23 17:27, Liu Shixin wrote: > Patch a873dfe1032a ("mm, hwpoison: try to recover from copy-on write faults") > introduced a new copy_user_highpage_mc() function, and fix the kernel crash > when the kernel is copying a normal page as the result of a copy-on-write > fault and runs into an uncorrectable error. But it doesn't work for HugeTLB.
Andrew asked about user-visible effects. Perhaps, a better way of stating this in the commit message might be:
Commit a873dfe1032a ("mm, hwpoison: try to recover from copy-on write faults") introduced the routine copy_user_highpage_mc() to gracefully handle copying of user pages with uncorrectable errors. Previously, such copies would result in a kernel crash. hugetlb has separate code paths for copy-on-write and does not benefit from the changes made in commit a873dfe1032a.
Modify hugetlb copy-on-write code paths to use copy_mc_user_highpage() so that they can also gracefully handle uncorrectable errors in user pages. This involves changing the hugetlb specific routine ?copy_user_folio()? from type void to int so that it can return an error. Modify the hugetlb userfaultfd code in the same way so that it can return -EHWPOISON if it encounters an uncorrectable error.
NOTE - There is still some churn in the series that introduces copy_user_folio() and the name may change.
> This is to support HugeTLB by using copy_mc_user_highpage() in copy_subpage() > and copy_user_gigantic_page() too. > > Moreover, this is also used by userfaultfd, it will return -EHWPOISON if > running into an uncorrectable error. > > Signed-off-by: Liu Shixin <liushixin2@huawei.com> > --- > include/linux/mm.h | 6 ++--- > mm/hugetlb.c | 19 +++++++++++---- > mm/memory.c | 59 +++++++++++++++++++++++++++++----------------- > 3 files changed, 56 insertions(+), 28 deletions(-)
Code changes look good to me.
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Related question perhaps for Tony not directly impacting this patch. This patch touches the hugetlb clear page paths withour consequence.
Just wondering if we can/should create something like clear_mc_user_highpage to address clearing pages as well? Apologies if this was previously discussed. -- Mike Kravetz
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