linux-kernel - Re: [PATCH] hugetlbfs: remove call to huge_pte_alloc without i_mmap

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Message-ID: <20200803225234.GD23808@casper.infradead.org>
Date:   Mon, 3 Aug 2020 23:52:34 +0100
From:   Matthew Wilcox <willy@...radead.org>
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] hugetlbfs: remove call to huge_pte_alloc without
 i_mmap_rwsem

On Mon, Aug 03, 2020 at 03:43:35PM -0700, Mike Kravetz wrote:
> Commit c0d0381ade79 ("hugetlbfs: use i_mmap_rwsem for more pmd sharing
> synchronization") requires callers of huge_pte_alloc to hold i_mmap_rwsem
> in at least read mode.  This is because the explicit locking in
> huge_pmd_share (called by huge_pte_alloc) was removed.  When restructuring
> the code, the call to huge_pte_alloc in the else block at the beginning
> of hugetlb_fault was missed.

Should we have a call to mmap_assert_locked() in huge_pte_alloc(),
at least the generic one?