From: Mike Kravetz <mike.kravetz@oracle.com>
To: Liu Shixin <liushixin2@huawei.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
Tony Luck <tony.luck@intel.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Muchun Song <muchun.song@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -next] mm: hwpoison: support recovery from HugePage copy-on-write faults
Date: Wed, 12 Apr 2023 11:13:50 -0700 [thread overview]
Message-ID: <20230412181350.GA22818@monkey> (raw)
In-Reply-To: <20230411092741.780679-1-liushixin2@huawei.com>
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
next prev parent reply other threads:[~2023-04-12 18:14 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-11 9:27 [PATCH -next] mm: hwpoison: support recovery from HugePage copy-on-write faults Liu Shixin
2023-04-12 0:26 ` Andrew Morton
2023-04-12 18:13 ` Mike Kravetz [this message]
2023-04-12 21:57 ` Andrew Morton
2023-04-12 22:21 ` Mike Kravetz
2023-04-12 22:56 ` Andrew Morton
2023-04-12 23:37 ` Mike Kravetz
2023-04-13 0:47 ` Luck, Tony
2023-04-13 1:55 ` Liu Shixin
2023-04-13 1:51 ` Liu Shixin
2023-04-13 1:49 ` Liu Shixin
2023-04-13 12:57 ` Jiaqi Yan
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