From: Miaohe Lin <linmiaohe@huawei.com>
To: Mike Kravetz <mike.kravetz@oracle.com>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>,
David Hildenbrand <david@redhat.com>,
Sven Schnelle <svens@linux.ibm.com>,
Michal Hocko <mhocko@suse.com>, Peter Xu <peterx@redhat.com>,
Naoya Horiguchi <naoya.horiguchi@linux.dev>,
"Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>,
Andrea Arcangeli <aarcange@redhat.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Davidlohr Bueso <dave@stgolabs.net>,
Prakash Sangappa <prakash.sangappa@oracle.com>,
James Houghton <jthoughton@google.com>,
Mina Almasry <almasrymina@google.com>,
Pasha Tatashin <pasha.tatashin@soleen.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Ray Fucillo <Ray.Fucillo@intersystems.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v2 9/9] hugetlb: clean up code checking for fault/truncation races
Date: Thu, 29 Sep 2022 14:25:16 +0800 [thread overview]
Message-ID: <cb068983-70d1-53a2-4175-e8ca7818126c@huawei.com> (raw)
In-Reply-To: <20220914221810.95771-10-mike.kravetz@oracle.com>
On 2022/9/15 6:18, Mike Kravetz wrote:
> With the new hugetlb vma lock in place, it can also be used to handle
> page fault races with file truncation. The lock is taken at the
> beginning of the code fault path in read mode. During truncation, it
> is taken in write mode for each vma which has the file mapped. The
> file's size (i_size) is modified before taking the vma lock to unmap.
>
> How are races handled?
>
> The page fault code checks i_size early in processing after taking the
> vma lock. If the fault is beyond i_size, the fault is aborted. If the
> fault is not beyond i_size the fault will continue and a new page will
> be added to the file. It could be that truncation code modifies i_size
> after the check in fault code. That is OK, as truncation code will soon
> remove the page. The truncation code will wait until the fault is
> finished, as it must obtain the vma lock in write mode.
As previous thread [1] points out, if vma->vm_private_data is NULL, there won't be any synchronization
which provides the same type of synchronization around i_size as provided by the fault mutex as in [2].
([2] will take the fault mutex for EVERY index in the truncated range)
[1] https://lore.kernel.org/lkml/YyOKIhygl66cG8Yr@monkey/T/#m6b69af9e8cdba01246c2b210bd044bf895b815ee
[2] https://lore.kernel.org/lkml/20220824175757.20590-5-mike.kravetz@oracle.com/
Except from that, this patch looks good to me. Thanks Mike.
Thanks,
Miaohe Lin
prev parent reply other threads:[~2022-09-29 6:25 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-14 22:18 [PATCH v2 0/9] hugetlb: Use new vma lock for huge pmd sharing synchronization Mike Kravetz
2022-09-14 22:18 ` [PATCH v2 1/9] hugetlbfs: revert use i_mmap_rwsem to address page fault/truncate race Mike Kravetz
2022-09-14 22:18 ` [PATCH v2 2/9] hugetlbfs: revert use i_mmap_rwsem for more pmd sharing synchronization Mike Kravetz
2022-09-14 22:18 ` [PATCH v2 3/9] hugetlb: rename remove_huge_page to hugetlb_delete_from_page_cache Mike Kravetz
2022-09-14 22:18 ` [PATCH v2 4/9] hugetlb: create remove_inode_single_folio to remove single file folio Mike Kravetz
2022-09-24 12:36 ` Miaohe Lin
2022-09-14 22:18 ` [PATCH v2 5/9] hugetlb: rename vma_shareable() and refactor code Mike Kravetz
2022-09-14 22:18 ` [PATCH v2 6/9] hugetlb: add vma based lock for pmd sharing Mike Kravetz
2022-09-15 20:25 ` Mike Kravetz
2022-09-24 13:11 ` Miaohe Lin
2022-09-14 22:18 ` [PATCH v2 7/9] hugetlb: create hugetlb_unmap_file_folio to unmap single file folio Mike Kravetz
2022-09-14 22:18 ` [PATCH v2 8/9] hugetlb: use new vma_lock for pmd sharing synchronization Mike Kravetz
2022-09-29 6:08 ` Miaohe Lin
2022-10-01 0:00 ` Mike Kravetz
2022-10-08 2:29 ` Miaohe Lin
2022-09-14 22:18 ` [PATCH v2 9/9] hugetlb: clean up code checking for fault/truncation races Mike Kravetz
2022-09-19 23:32 ` Mike Kravetz
2022-09-29 6:25 ` Miaohe Lin [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=cb068983-70d1-53a2-4175-e8ca7818126c@huawei.com \
--to=linmiaohe@huawei.com \
--cc=Ray.Fucillo@intersystems.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=almasrymina@google.com \
--cc=aneesh.kumar@linux.vnet.ibm.com \
--cc=axelrasmussen@google.com \
--cc=dave@stgolabs.net \
--cc=david@redhat.com \
--cc=jthoughton@google.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=mike.kravetz@oracle.com \
--cc=naoya.horiguchi@linux.dev \
--cc=pasha.tatashin@soleen.com \
--cc=peterx@redhat.com \
--cc=prakash.sangappa@oracle.com \
--cc=songmuchun@bytedance.com \
--cc=svens@linux.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).