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([122.171.16.167]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82f8ebcc9easm7211169b3a.39.2026.04.18.10.18.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 Apr 2026 10:18:14 -0700 (PDT) From: Sunny Patel To: david@kernel.org Cc: akpm@linux-foundation.org, apopple@nvidia.com, byungchul@sk.com, gourry@gourry.net, joshua.hahnjy@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, matthew.brost@intel.com, nueralspacetech@gmail.com, rakie.kim@sk.com, sj@kernel.org, ying.huang@linux.alibaba.com, ziy@nvidia.com Subject: Re: [PATCH] mm/migrate_device: Cleanup up PMD Checks and warnings Date: Sat, 18 Apr 2026 22:48:06 +0530 Message-ID: <20260418171806.11615-1-nueralspacetech@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <82193ab8-e6f6-4664-8b4f-e30d280d8b1c@kernel.org> References: <82193ab8-e6f6-4664-8b4f-e30d280d8b1c@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On 4/17/26 01:52, SeongJae Park wrote: > On Thu, 16 Apr 2026 21:44:15 +0200 "David Hildenbrand (Arm)" wrote: > >> On 4/14/26 16:13, Sunny Patel wrote: > [...] >>> @@ -865,12 +864,13 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate, >>> if (userfaultfd_missing(vma)) >>> goto unlock_abort; >>> >>> - if (!pmd_none(*pmdp)) { >>> + if (pmd_present(*pmdp)) { >>> if (!is_huge_zero_pmd(*pmdp)) >>> goto unlock_abort; >>> flush = true; >>> - } else if (!pmd_none(*pmdp)) >>> + } else if (!pmd_none(*pmdp)) { >>> goto unlock_abort; >>> + } >>> >>> add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); >>> folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE); >> >> is_huge_zero_pmd() checks pmd_present(), so we didn't have a bug before. >> >> We could also do: >> >> if (is_huge_zero_pmd(*pmdp)) { >> flush = true; >> } else if (!pmd_none(*pmdp)) { >> goto unlock_abort; >> } > > Then we could even further remove the braces and reduce one more line, nice! is_huge_zero_pmd() didn't check for pmd_present as of now as per the current implementation of it so additional check require for pmd_present(). Please let me know if anything needs to add in here. Thanks, Sunny Patel