linux-kernel - Re: [RFC PATCH v2 05/47] hugetlb: make hugetlb_vma_lock

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Message-ID: <Y5O4hEVoT3/sdnk4@monkey>
Date:   Fri, 9 Dec 2022 14:36:52 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     James Houghton <jthoughton@...gle.com>
Cc:     Muchun Song <songmuchun@...edance.com>,
        Peter Xu <peterx@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Zach O'Keefe <zokeefe@...gle.com>,
        Manish Mishra <manish.mishra@...anix.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 05/47] hugetlb: make hugetlb_vma_lock_alloc return
 its failure reason

On 10/21/22 16:36, James Houghton wrote:
> Currently hugetlb_vma_lock_alloc doesn't return anything, as there is no
> need: if it fails, PMD sharing won't be enabled. However, HGM requires
> that the VMA lock exists, so we need to verify that
> hugetlb_vma_lock_alloc actually succeeded. If hugetlb_vma_lock_alloc
> fails, then we can pass that up to the caller that is attempting to
> enable HGM.

No serious objections to this change ...

However, there are currently only two places today where hugetlb_vma_lock_alloc
is called: hugetlb_reserve_pages and hugetlb_vm_op_open.  hugetlb_reserve_pages
is not an issue.  Since hugetlb_vm_op_open (as a defined vm_operation) returns
void, I am not sure how you plan to pass up an allocation failure.
Suspect this will become evident in subsequent patches.
-- 
Mike Kravetz