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Hallyn" , David Rientjes , Rik van Riel , Mel Gorman , Michel Lespinasse , Tang Chen , Robin Holt , Shaohua Li , Sasha Levin , Minchan Kim Subject: Re: [PATCH v8 1/3] mm: rearrange madvise code to allow for reuse Message-ID: References: <20210827191858.2037087-1-surenb@google.com> <20210827191858.2037087-2-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210827191858.2037087-2-surenb@google.com> User-Agent: Mutt/2.0.7 (2021-05-04) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 27, 2021 at 12:18:56PM -0700, Suren Baghdasaryan wrote: ... > > +/* > + * Apply an madvise behavior to a region of a vma. madvise_update_vma > + * will handle splitting a vm area into separate areas, each area with its own > + * behavior. > + */ > +static int madvise_vma_behavior(struct vm_area_struct *vma, > + struct vm_area_struct **prev, > + unsigned long start, unsigned long end, > + unsigned long behavior) > +{ > + int error = 0; Hi Suren! A nitpick -- this variable is never used with default value so I think we could drop assignment here. ... > + case MADV_DONTFORK: > + new_flags |= VM_DONTCOPY; > + break; > + case MADV_DOFORK: > + if (vma->vm_flags & VM_IO) { > + error = -EINVAL; We can exit early here, without jumping to the end of the function, right? > + goto out; > + } > + new_flags &= ~VM_DONTCOPY; > + break; > + case MADV_WIPEONFORK: > + /* MADV_WIPEONFORK is only supported on anonymous memory. */ > + if (vma->vm_file || vma->vm_flags & VM_SHARED) { > + error = -EINVAL; And here too. > + goto out; > + } > + new_flags |= VM_WIPEONFORK; > + break; > + case MADV_KEEPONFORK: > + new_flags &= ~VM_WIPEONFORK; > + break; > + case MADV_DONTDUMP: > + new_flags |= VM_DONTDUMP; > + break; > + case MADV_DODUMP: > + if (!is_vm_hugetlb_page(vma) && new_flags & VM_SPECIAL) { > + error = -EINVAL; Same. > + goto out; > + } > + new_flags &= ~VM_DONTDUMP; > + break; > + case MADV_MERGEABLE: > + case MADV_UNMERGEABLE: > + error = ksm_madvise(vma, start, end, behavior, &new_flags); > + if (error) > + goto out; > + break; > + case MADV_HUGEPAGE: > + case MADV_NOHUGEPAGE: > + error = hugepage_madvise(vma, &new_flags, behavior); > + if (error) > + goto out; > + break; > + } > + > + error = madvise_update_vma(vma, prev, start, end, new_flags); > + > +out: I suppose we better keep the former comment on why we maps ENOMEM to EAGAIN? Cyrill