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Sat, 28 Mar 2026 12:45:19 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Suren Baghdasaryan Date: Sat, 28 Mar 2026 12:45:08 -0700 X-Gm-Features: AQROBzBe7wmE_LywvyOSjvh0vtGoVDqrkmnr6QHNpG3Sc1BM2A4FO5RBot8Ad3s Message-ID: Subject: Re: [PATCH v3 12/13] mm/huge_memory: add and use normal_or_softleaf_folio_pmd() To: "Lorenzo Stoakes (Oracle)" Cc: Andrew Morton , David Hildenbrand , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Michal Hocko , Kiryl Shutsemau , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Stat-Signature: a4acramcs3q16oxc7hcay6fnyiqocaf7 X-Rspamd-Queue-Id: C6635140009 X-Rspamd-Server: rspam09 X-HE-Tag: 1774727120-543719 X-HE-Meta: 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 xOOBDBLS nFLsh8ucerfY02S7pxzXyVoCZcdr9THmRSk4hvqi1xIzv9JksD7a3JwvvjJWwBN5aQj2P+jP9JvatJAIkY+jpQkAByFhAwvJQUizK+1bN45gF5ixe2UgxXAbIrSujFURZCOhZkDOTN6jqvP3PxalxGDhEA2Xan7oyiJfwaA5E/VwwCQa1NwJcMwG4aMXY/9rdJIOFLzhAPWHTkm4Qr7rEuqBkm8Eh2zb8t+uTo8+kHPi75w9vmqnoq7isy7/YouyqsxZxFRGBM7Fxw1/JOJXkawcowcxdZ2SVvjccDEdxf4eI3NUQhgsmRqTxuIC5RMKRo4JBPGZPY9f/tBwGQSpXpbgoV5zIS1dR3c6ZvCkexYoaaQ2xZ59yysaZ1VPxyNHJiNz9 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Mar 20, 2026 at 11:08=E2=80=AFAM Lorenzo Stoakes (Oracle) wrote: > > Now we have pmd_to_softleaf_folio() available to us which also raises a > CONFIG_DEBUG_VM warning if unexpectedly an invalid softleaf entry, we can > now abstract folio handling altogether. > > vm_normal_folio() deals with the huge zero page (which is present), as we= ll > as PFN map/mixed map mappings in both cases returning NULL. > > Otherwise, we try to obtain the softleaf folio. > > This makes the logic far easier to comprehend and has it use the standard > vm_normal_folio_pmd() path for decoding of present entries. > > Finally, we have to update the flushing logic to only do so if a folio is > established. > > This patch also makes the 'is_present' value more accurate - because PFN > map, mixed map and zero huge pages are present, just not present and > 'normal'. > > Signed-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Suren Baghdasaryan One clarifying question below but I think I know the answer, just want to double-check. > --- > mm/huge_memory.c | 47 +++++++++++++++++++---------------------------- > 1 file changed, 19 insertions(+), 28 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 9ddf38d68406..5831966391bd 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2342,10 +2342,6 @@ static void zap_huge_pmd_folio(struct mm_struct *m= m, struct vm_area_struct *vma, > add_mm_counter(mm, mm_counter_file(folio), > -HPAGE_PMD_NR); > > - /* > - * Use flush_needed to indicate whether the PMD entry > - * is present, instead of checking pmd_present() again. > - */ > if (is_present && pmd_young(pmdval) && > likely(vma_has_recency(vma))) > folio_mark_accessed(folio); > @@ -2356,6 +2352,17 @@ static void zap_huge_pmd_folio(struct mm_struct *m= m, struct vm_area_struct *vma, > folio_put(folio); > } > > +static struct folio *normal_or_softleaf_folio_pmd(struct vm_area_struct = *vma, > + unsigned long addr, pmd_t pmdval, bool is_present) > +{ > + if (is_present) > + return vm_normal_folio_pmd(vma, addr, pmdval); > + > + if (!thp_migration_supported()) > + WARN_ONCE(1, "Non present huge pmd without pmd migration = enabled!"); > + return pmd_to_softleaf_folio(pmdval); > +} > + > /** > * zap_huge_pmd - Zap a huge THP which is of PMD size. > * @tlb: The MMU gather TLB state associated with the operation. > @@ -2390,36 +2397,20 @@ bool zap_huge_pmd(struct mmu_gather *tlb, struct = vm_area_struct *vma, > tlb->fullmm); > arch_check_zapped_pmd(vma, orig_pmd); > tlb_remove_pmd_tlb_entry(tlb, pmd, addr); > - if (vma_is_special_huge(vma)) > - goto out; > - if (is_huge_zero_pmd(orig_pmd)) { > - if (!vma_is_dax(vma)) > - has_deposit =3D true; > - goto out; > - } > > - if (pmd_present(orig_pmd)) { > - folio =3D pmd_folio(orig_pmd); > - is_present =3D true; > - } else if (pmd_is_valid_softleaf(orig_pmd)) { > - const softleaf_t entry =3D softleaf_from_pmd(orig_pmd); > + is_present =3D pmd_present(orig_pmd); nit: With this you don't need to initialize is_present anymore when you define it. > + folio =3D normal_or_softleaf_folio_pmd(vma, addr, orig_pmd, is_pr= esent); > + if (folio) > + zap_huge_pmd_folio(mm, vma, orig_pmd, folio, is_present, > + &has_deposit); > + else if (is_huge_zero_pmd(orig_pmd)) > + has_deposit =3D !vma_is_dax(vma); > > - folio =3D softleaf_to_folio(entry); > - if (!thp_migration_supported()) > - WARN_ONCE(1, "Non present huge pmd without pmd mi= gration enabled!"); > - } else { > - WARN_ON_ONCE(true); > - goto out; > - } > - > - zap_huge_pmd_folio(mm, vma, orig_pmd, folio, is_present, &has_dep= osit); > - > -out: > if (has_deposit) > zap_deposited_table(mm, pmd); > > spin_unlock(ptl); > - if (is_present) > + if (is_present && folio) In which case would you have a valid folio and !is_present? Is that the softleaf case? > tlb_remove_page_size(tlb, &folio->page, HPAGE_PMD_SIZE); > return true; > } > -- > 2.53.0 >