Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:4 as permitted sender) client-ip=2620:137:e000::3:4;
Date:   Mon, 25 Sep 2023 23:52:37 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Hugh Dickins <hughd@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Andi Kleen <ak@linux.intel.com>,
        Christoph Lameter <cl@linux.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        David Hildenbrand <david@redhat.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Yang Shi <shy828301@gmail.com>,
        Sidhartha Kumar <sidhartha.kumar@oracle.com>,
        Vishal Moola <vishal.moola@gmail.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Tejun Heo <tj@kernel.org>,
        Mel Gorman <mgorman@techsingularity.net>,
        Michal Hocko <mhocko@suse.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH 08/12] mempolicy: remove confusing MPOL_MF_LAZY dead code
Message-ID: <ZRIPNSRSDH2PfG74@casper.infradead.org>
References: <2d872cef-7787-a7ca-10e-9d45a64c80b4@google.com>
 <2cb8b08a-a96c-2a61-94dd-4cd51ad0605d@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <2cb8b08a-a96c-2a61-94dd-4cd51ad0605d@google.com>
Precedence: bulk

On Mon, Sep 25, 2023 at 01:30:51AM -0700, Hugh Dickins wrote:
> v3.8 commit b24f53a0bea3 ("mm: mempolicy: Add MPOL_MF_LAZY") introduced
> MPOL_MF_LAZY, and included it in the MPOL_MF_VALID flags; but a720094ded8
> ("mm: mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from userspace for now")
> immediately removed it from MPOL_MF_VALID flags, pending further review.
> "This will need to be revisited", but it has not been reinstated.
> 
> The present state is confusing: there is dead code in mm/mempolicy.c to
> handle MPOL_MF_LAZY cases which can never occur.  Remove that: it can be
> resurrected later if necessary.  But keep the definition of MPOL_MF_LAZY,
> which must remain in the UAPI, even though it always fails with EINVAL.
> 
> https://lore.kernel.org/linux-mm/1553041659-46787-1-git-send-email-yang.shi@linux.alibaba.com/
> links to a previous request to remove MPOL_MF_LAZY.
> 
> Signed-off-by: Hugh Dickins <hughd@google.com>

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>