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Thu, 26 Jan 2023 08:11:39 -0800 (PST) MIME-Version: 1.0 References: <20230125233554.153109-1-surenb@google.com> <20230125233554.153109-6-surenb@google.com> <20230126151923.4fu34ytwkpbbnvha@techsingularity.net> In-Reply-To: <20230126151923.4fu34ytwkpbbnvha@techsingularity.net> From: Suren Baghdasaryan Date: Thu, 26 Jan 2023 08:11:28 -0800 Message-ID: Subject: Re: [PATCH v3 5/7] mm: replace vma->vm_flags indirect modification in ksm_madvise To: Mel Gorman Cc: akpm@linux-foundation.org, michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org, mingo@redhat.com, will@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, hughlynch@google.com, leewalsh@google.com, posk@google.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 26, 2023 at 7:19 AM Mel Gorman wrote: > > On Wed, Jan 25, 2023 at 03:35:52PM -0800, Suren Baghdasaryan wrote: > > Replace indirect modifications to vma->vm_flags with calls to modifier > > functions to be able to track flag changes and to keep vma locking > > correctness. > > > > Signed-off-by: Suren Baghdasaryan > > Acked-by: Michal Hocko > > --- > > arch/powerpc/kvm/book3s_hv_uvmem.c | 5 ++++- > > arch/s390/mm/gmap.c | 5 ++++- > > 2 files changed, 8 insertions(+), 2 deletions(-) > > > > diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c > > index 1d67baa5557a..325a7a47d348 100644 > > --- a/arch/powerpc/kvm/book3s_hv_uvmem.c > > +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c > > @@ -393,6 +393,7 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm, > > { > > unsigned long gfn = memslot->base_gfn; > > unsigned long end, start = gfn_to_hva(kvm, gfn); > > + unsigned long vm_flags; > > int ret = 0; > > struct vm_area_struct *vma; > > int merge_flag = (merge) ? MADV_MERGEABLE : MADV_UNMERGEABLE; > > @@ -409,12 +410,14 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm, > > ret = H_STATE; > > break; > > } > > + vm_flags = vma->vm_flags; > > ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, > > - merge_flag, &vma->vm_flags); > > + merge_flag, &vm_flags); > > if (ret) { > > ret = H_STATE; > > break; > > } > > + reset_vm_flags(vma, vm_flags); > > start = vma->vm_end; > > } while (end > vma->vm_end); > > Add a comment on why the vm_flags are copied in case someone "optimises" > this in the future? Something like > > /* Copy vm_flags to avoid any partial modifications in ksm_madvise. */ Ack. > > > > > diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c > > index 3a695b8a1e3c..d5eb47dcdacb 100644 > > --- a/arch/s390/mm/gmap.c > > +++ b/arch/s390/mm/gmap.c > > @@ -2587,14 +2587,17 @@ int gmap_mark_unmergeable(void) > > { > > struct mm_struct *mm = current->mm; > > struct vm_area_struct *vma; > > + unsigned long vm_flags; > > int ret; > > VMA_ITERATOR(vmi, mm, 0); > > > > for_each_vma(vmi, vma) { > > + vm_flags = vma->vm_flags; > > ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, > > - MADV_UNMERGEABLE, &vma->vm_flags); > > + MADV_UNMERGEABLE, &vm_flags); > > if (ret) > > return ret; > > + reset_vm_flags(vma, vm_flags); > > Same. > > Not necessary as such as there are few users of ksm_madvise and I doubt > it'll introduce new surprises. > > With or without the comment; > > Acked-by: Mel Gorman Thanks! > > -- > Mel Gorman > SUSE Labs