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Howlett" , Suren Baghdasaryan , Matthew Wilcox , David Hildenbrand , Pedro Falcato , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 01/10] mm/mremap: introduce more mergeable mremap via MREMAP_RELOCATE_ANON Message-ID: <20250430004703.63rumj4znewlbc2h@master> Reply-To: Wei Yang References: <87e668d54927bb4ccdb7d374275e0662de667697.1745307301.git.lorenzo.stoakes@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87e668d54927bb4ccdb7d374275e0662de667697.1745307301.git.lorenzo.stoakes@oracle.com> User-Agent: NeoMutt/20170113 (1.7.2) On Tue, Apr 22, 2025 at 09:09:20AM +0100, Lorenzo Stoakes wrote: [...] >+bool vma_had_uncowed_children(struct vm_area_struct *vma) >+{ >+ struct anon_vma *anon_vma = vma ? vma->anon_vma : NULL; >+ bool ret; >+ >+ if (!anon_vma) >+ return false; >+ >+ /* >+ * If we're mmap locked then there's no way for this count to change, as >+ * any such change would require this lock not be held. >+ */ >+ if (rwsem_is_locked(&vma->vm_mm->mmap_lock)) >+ return anon_vma->num_children > 1; Hi, Lorenzo May I have a question here? >+ >+ /* >+ * Any change that would increase the number of children would be >+ * prevented by a read lock. >+ */ >+ anon_vma_lock_read(anon_vma); >+ ret = anon_vma->num_children > 1; >+ anon_vma_unlock_read(anon_vma); >+ >+ return ret; >+} -- Wei Yang Help you, Help me