From: Mike Kravetz <mike.kravetz@oracle.com>
To: Larry Bassel <larry.bassel@oracle.com>,
Matthew Wilcox <willy@infradead.org>
Cc: dan.j.williams@intel.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org
Subject: Re: [PATCH, RFC 2/2] Implement sharing/unsharing of PMDs for FS/DAX
Date: Fri, 10 May 2019 15:45:04 -0700 [thread overview]
Message-ID: <af218b46-ece3-1189-e43c-209ec5cf1022@oracle.com> (raw)
In-Reply-To: <20190510161607.GB27674@ubuette>
On 5/10/19 9:16 AM, Larry Bassel wrote:
> On 09 May 19 09:49, Matthew Wilcox wrote:
>> On Thu, May 09, 2019 at 09:05:33AM -0700, Larry Bassel wrote:
>>> This is based on (but somewhat different from) what hugetlbfs
>>> does to share/unshare page tables.
>>
>> Wow, that worked out far more cleanly than I was expecting to see.
>
> Yes, I was pleasantly surprised. As I've mentioned already, I
> think this is at least partially due to the nature of DAX.
I have not looked in detail to make sure this is indeed all the places you
need to hook and special case for sharing/unsharing. Since this scheme is
somewhat like that used for hugetlb, I just wanted to point out some nasty
bugs related to hugetlb PMD sharing that were fixed last year.
5e41540c8a0f hugetlbfs: fix kernel BUG at fs/hugetlbfs/inode.c:444!
dff11abe280b hugetlb: take PMD sharing into account when flushing tlb/caches
017b1660df89 mm: migration: fix migration of huge PMD shared pages
The common issue in these is that when unmapping a page with a shared PMD
mapping you need to flush the entire shared range and not just the unmapped
page. The above changes were hugetlb specific. I do not know if any of
this applies in the case of DAX.
--
Mike Kravetz
next prev parent reply other threads:[~2019-05-10 22:45 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-09 16:05 [PATCH, RFC 0/2] Share PMDs for FS/DAX on x86 Larry Bassel
2019-05-09 16:05 ` [PATCH, RFC 1/2] Add config option to enable FS/DAX PMD sharing Larry Bassel
2019-05-10 16:32 ` Elliott, Robert (Servers)
2019-05-10 18:14 ` Dan Williams
2019-05-09 16:05 ` [PATCH, RFC 2/2] Implement sharing/unsharing of PMDs for FS/DAX Larry Bassel
2019-05-09 16:49 ` Matthew Wilcox
2019-05-10 16:16 ` Larry Bassel
2019-05-10 22:45 ` Mike Kravetz [this message]
2019-05-14 13:01 ` Kirill A. Shutemov
2019-05-24 16:07 ` Larry Bassel
2019-05-24 17:02 ` Dan Williams
2019-06-12 2:07 ` Kirill A. Shutemov
2019-05-14 12:28 ` [PATCH, RFC 0/2] Share PMDs for FS/DAX on x86 Kirill A. Shutemov
2019-05-14 16:09 ` Larry Bassel
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