linux-kernel - Re: [PATCH v2 2/2] hugetlbfs: Use i_mmap_rwsem to fix page fault/truncate race

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Message-ID: <20181221102824.5v36l6l5t2zthpgr@kshutemo-mobl1>
Date:   Fri, 21 Dec 2018 13:28:24 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Michal Hocko <mhocko@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Prakash Sangappa <prakash.sangappa@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH v2 2/2] hugetlbfs: Use i_mmap_rwsem to fix page
 fault/truncate race

On Tue, Dec 18, 2018 at 02:35:57PM -0800, Mike Kravetz wrote:
> Instead of writing the required complicated code for this rare
> occurrence, just eliminate the race.  i_mmap_rwsem is now held in read
> mode for the duration of page fault processing.  Hold i_mmap_rwsem
> longer in truncation and hold punch code to cover the call to
> remove_inode_hugepages.

One of remove_inode_hugepages() callers is noticeably missing --
hugetlbfs_evict_inode(). Why?

It at least deserves a comment on why the lock rule doesn't apply to it.

-- 
 Kirill A. Shutemov