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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qkuRR-0048aP-JD; Mon, 25 Sep 2023 22:52:37 +0000 Date: Mon, 25 Sep 2023 23:52:37 +0100 From: Matthew Wilcox To: Hugh Dickins Cc: Andrew Morton , Andi Kleen , Christoph Lameter , Mike Kravetz , David Hildenbrand , Suren Baghdasaryan , Yang Shi , Sidhartha Kumar , Vishal Moola , Kefeng Wang , Greg Kroah-Hartman , Tejun Heo , Mel Gorman , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 08/12] mempolicy: remove confusing MPOL_MF_LAZY dead code Message-ID: 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> X-Rspamd-Queue-Id: 0263CC000F X-Rspam-User: X-Stat-Signature: oprr8bmtiy6nget1osu9cz13qy7m5s7y X-Rspamd-Server: rspam01 X-HE-Tag: 1695682379-740332 X-HE-Meta: U2FsdGVkX1+MY2A3YQOqfWktXylMVQJ6e47c3Vaahp7rbx/f2kMAFns/7DNWV3m+0KE8MRLqIInKePWKLQa2Tw++5DsDStxPOkMRsM+48RwiBmLaYCoo40yB86NLz/FVGlKGd7XX+e1hs8ln3SAUENlAXu4Kmn3Y7K6opSYWXZemZEJZcXw+5qPEkh61zzfw/nZ04NmOjjNcYyM1wxiU2e4IgxE3s06IhE6++cuCC0YbZIKXLdOGMMiaguTnTjVTzkF3UxhRECiEIJwcDdqyFNNhfEKcI+eaD5gxKRiUMsZRhKrVH229uenJEHKO9GEYXuq7SzSX1HKclwVjDx4n27b0l4il6kcfoLo21FhZ7hAa/yItdt8Yf5K0pbgq3m4Vs0dPoLgXyer+yEVbAcf/xQat+QUAT+C5GvdefnJFnBm7CBR00gPIHWhVeACvqMlZ2Et7F4TSTvaU3rpaknPLhg5E6HThSBthojHtsdMFN5kxt4TsRMLMy7WzlRwABVlle2MduJTwmHqn9SnjYutydSW4nVcv7xV61cWApyEa++XL8ZAoZRHtDTEd5d3hC78LwWjwC+Ajlz8Q7m8xNEtKy8N6dLSTyPTCS6DcAM8Y9FiA9BsN1/vzSX+OKi18jc+CFoiFpdBBBKqaaoqu8kzhw6oOnDy162FhWwehTsakfLcYdUB0nS7j5ls1pqXu15oY3XuBDiUUXc1Bn3YSWLfUyVvFkTn50pcnj2QxOGuN9KH5WMbPXy3KSz1QBnrltVfQ/u4UQ1xml9vJY8gScTolqoGrSEc+rMcYSjjUud7now8ZKt3aeE8DORZt2fu4O3yY9tl2EG3OqPgXTTYWtoszheLtHW0fgSeUyPgecrSwpxqbTDtccnO9Mt98bPciWS2BiV4w7b+P52PEGKdirUkps2b4UJw5aXg3BDIk+RIzavg+l3QOpGcBTH1lB8Iitjd/cie0tZYH0+LKqd8OkiZ oz2cOZNB B9AVBFPBMS/xT+FtuNkhxDRyeuxCp+NT6piEjuJ8yYbOzIVjwonrR9PFgDM3yvGCiqFiMEpKMZfFxgrj/cUS+octPiE4oHuhnqg9ioSCgszKE9h1oksofYdb9yGz0xTEqNUz6f0cPLiB+orANo5SP5lT3dimT8cJqbkUoN5DfH0VH/gjeFyxbLyq67gnlC6AoXxvXGX/17UG005DpK1mNdsKlvBs1o++lXQlIkrKPlvv61lCDSaPewcpsSrSS8VaHmz8VojLQimNvLe7g0Rb58KrVR22XXnH2rxk7o3Fklko1i7oCIS3jF/YUQOzKaATF13uK05Ot2RRikXgkvuVZhgQta73uCgYT6rnIiaganjuFUFGCPAGmjpFIWFTQGTqbvwyjvzfFfjS6srz//Nzww6FXt55CxvoMP+hO X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 Reviewed-by: Matthew Wilcox (Oracle)