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Tue, 03 Oct 2023 15:28:17 -0700 (PDT) MIME-Version: 1.0 References: <80c9665c-1c3f-17ba-21a3-f6115cebf7d@google.com> In-Reply-To: <80c9665c-1c3f-17ba-21a3-f6115cebf7d@google.com> From: Yang Shi Date: Tue, 3 Oct 2023 15:28:06 -0700 Message-ID: Subject: Re: [PATCH v2 08/12] mempolicy: remove confusing MPOL_MF_LAZY dead code To: Hugh Dickins Cc: Andrew Morton , Andi Kleen , Christoph Lameter , Matthew Wilcox , Mike Kravetz , David Hildenbrand , Suren Baghdasaryan , Sidhartha Kumar , Vishal Moola , Kefeng Wang , Greg Kroah-Hartman , Tejun Heo , Mel Gorman , Michal Hocko , "Huang, Ying" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C829B1C001C X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 91imaffscni4bmsw6r9mh9ezn9jke7t6 X-HE-Tag: 1696372098-703473 X-HE-Meta: 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 dQev755e 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 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 Tue, Oct 3, 2023 at 2:24=E2=80=AFAM Hugh Dickins wrot= e: > > 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.s= hi@linux.alibaba.com/ > links to a previous request to remove MPOL_MF_LAZY. Thanks for mentioning my work. I'm glad to see the dead code go away. Reviewed-by: Yang Shi > > Signed-off-by: Hugh Dickins > Reviewed-by: Matthew Wilcox (Oracle) > --- > include/uapi/linux/mempolicy.h | 2 +- > mm/mempolicy.c | 18 ------------------ > 2 files changed, 1 insertion(+), 19 deletions(-) > > diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolic= y.h > index 046d0ccba4cd..a8963f7ef4c2 100644 > --- a/include/uapi/linux/mempolicy.h > +++ b/include/uapi/linux/mempolicy.h > @@ -48,7 +48,7 @@ enum { > #define MPOL_MF_MOVE (1<<1) /* Move pages owned by this process to co= nform > to policy */ > #define MPOL_MF_MOVE_ALL (1<<2) /* Move every page to conform to = policy */ > -#define MPOL_MF_LAZY (1<<3) /* Modifies '_MOVE: lazy migrate on faul= t */ > +#define MPOL_MF_LAZY (1<<3) /* UNSUPPORTED FLAG: Lazy migrate on faul= t */ > #define MPOL_MF_INTERNAL (1<<4) /* Internal flags start here */ > > #define MPOL_MF_VALID (MPOL_MF_STRICT | \ > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 5d99fd5cd60b..f3224a8b0f6c 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -636,12 +636,6 @@ unsigned long change_prot_numa(struct vm_area_struct= *vma, > > return nr_updated; > } > -#else > -static unsigned long change_prot_numa(struct vm_area_struct *vma, > - unsigned long addr, unsigned long end) > -{ > - return 0; > -} > #endif /* CONFIG_NUMA_BALANCING */ > > static int queue_pages_test_walk(unsigned long start, unsigned long end, > @@ -680,14 +674,6 @@ static int queue_pages_test_walk(unsigned long start= , unsigned long end, > if (endvma > end) > endvma =3D end; > > - if (flags & MPOL_MF_LAZY) { > - /* Similar to task_numa_work, skip inaccessible VMAs */ > - if (!is_vm_hugetlb_page(vma) && vma_is_accessible(vma) && > - !(vma->vm_flags & VM_MIXEDMAP)) > - change_prot_numa(vma, start, endvma); > - return 1; > - } > - > /* > * Check page nodes, and queue pages to move, in the current vma. > * But if no moving, and no strict checking, the scan can be skip= ped. > @@ -1274,9 +1260,6 @@ static long do_mbind(unsigned long start, unsigned = long len, > if (IS_ERR(new)) > return PTR_ERR(new); > > - if (flags & MPOL_MF_LAZY) > - new->flags |=3D MPOL_F_MOF; > - > /* > * If we are using the default policy then operation > * on discontinuous address spaces is okay after all > @@ -1321,7 +1304,6 @@ static long do_mbind(unsigned long start, unsigned = long len, > > if (!err) { > if (!list_empty(&pagelist)) { > - WARN_ON_ONCE(flags & MPOL_MF_LAZY); > nr_failed |=3D migrate_pages(&pagelist, new_folio= , NULL, > start, MIGRATE_SYNC, MR_MEMPOLICY_MBIND, = NULL); > } > -- > 2.35.3 >