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AJvYcCX+kq0zPmnGkJGt0AsxjOmVwi/UPSJw0D8C3b9o5GQqlSiVIuvVPGK/lhgq4oM58V/e3AeZ69mUaQ==@kvack.org X-Gm-Message-State: AOJu0Yybf6zfJaYjswwpmhDRbhz8lSByh9KNIIkKs62Svx0OOdwL75Bv 4nsdrJJ3GHRMOEHmGmSN2s8Nfz1JhodxSverTm6PsL7XFdUcrp2pyVD8r/I0L9a1i2hAXmMazSN v8Jt1Dl+vZRnbj+icJxg5aBtrHrpxkm1HjFXE X-Gm-Gg: ASbGncu1tIkMtY3G0I+4AI3Gqv62o5c9RcmT1im3LIAdipEoSueMH9bvccEpFMRC+CR 1exFjmb7k2N0lkuyKkzchje28L0AfplB9/EGUtwQV0cgrF6nazlCVDNy2QJJ7cowLDwFGCLeKg6 xP+RN3L2/BLcPqHE4D8ow= X-Google-Smtp-Source: AGHT+IGR3MiDuSLCkk9Qtb5XOWWGAH0Mo/U0wnQNxsfNM8PjCwxBAhMYvhJBGAUgmLFnUx/IZQSj0sU91hcEaY8VXfk= X-Received: by 2002:ac8:7f16:0:b0:486:a185:3136 with SMTP id d75a77b69052e-48aea463afcmr9349001cf.14.1746203018878; Fri, 02 May 2025 09:23:38 -0700 (PDT) MIME-Version: 1.0 References: <20250501044325.20365-1-fvdl@google.com> In-Reply-To: From: Frank van der Linden Date: Fri, 2 May 2025 09:23:26 -0700 X-Gm-Features: ATxdqUHj_L8a6Ckb7SPQieRfDhQiYlRdvto5IvmmBDSviiGHnvw16yspTg9HxXY Message-ID: Subject: Re: [PATCH] mm/hugetlb: copy the CMA flag when demoting To: Anshuman Khandual Cc: akpm@linux-foundation.org, muchun.song@linux.dev, linux-mm@kvack.org, osalvador@suse.de Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 102BE1C000B X-Stat-Signature: dq46x6amx5uyae5rzjg3c755d6hzqrq5 X-Rspam-User: X-HE-Tag: 1746203019-66610 X-HE-Meta: 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 AKY7JKg2 EJ45AbCiriV0//BTGjcrc7yW/Ua4fhfKPWw76Q4BybuUW9jfF1gkOMO8yX7OVIwtOwY4hEfky0x6/855VcMbokTZhIkV7RkGXuYhMBtb1FfOltYnRrlv/LU3t26Ge0HChBZn9lgKDXsPmMQNlL+7f2Br1FR+bSbMjBQEWhg16U+gOm70JKRr2lWfJm2ph6GjEd/QjUdgYajF4Ojs4ahTintlXtbmTlTvSI0TG/4ek7uHEloOueJOUBOmvYGVqCKJNQk2uN7P8BI9uc3OkZgNi1tYyPA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, May 2, 2025 at 1:27=E2=80=AFAM Anshuman Khandual wrote: > > > > On 5/1/25 10:13, Frank van der Linden wrote: > > Since commit d2d786714080 ("mm/hugetlb: enable bootmem allocation > > from CMA areas"), a flag is used to mark hugetlb folios as allocated > > from CMA. This flag is also used to decide if it should be freed > > to CMA. > > > > However, the flag isn't copied to the smaller folios when a hugetlb > > folio is broken up for demotion, which would cause it to be freed > > incorrectly. > > > > Fix this by copying the flag to the smaller order hugetlb pages > > created from the original one. > > > > Fixes: d2d786714080 ("mm/hugetlb: enable bootmem allocation from CMA ar= eas") > > Signed-off-by: Frank van der Linden > > --- > > mm/hugetlb.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index e3e6ac991b9c..6ea1be71aa42 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -4034,10 +4034,13 @@ static long demote_free_hugetlb_folios(struct h= state *src, struct hstate *dst, > > > > list_for_each_entry_safe(folio, next, src_list, lru) { > > int i; > > + bool cma; > > > > if (folio_test_hugetlb_vmemmap_optimized(folio)) > > continue; > > > > + cma =3D folio_test_hugetlb_cma(folio); > > + > > list_del(&folio->lru); > > > > split_page_owner(&folio->page, huge_page_order(src), huge= _page_order(dst)); > > @@ -4053,6 +4056,9 @@ static long demote_free_hugetlb_folios(struct hst= ate *src, struct hstate *dst, > > > > new_folio->mapping =3D NULL; > > init_new_hugetlb_folio(dst, new_folio); > > + /* Copy the CMA flag so that it is freed correctl= y */ > > + if (cma) > > + folio_set_hugetlb_cma(new_folio); > > list_add(&new_folio->lru, &dst_list); > > } > > } > > Agree with Oscar that HPG_cma need documentation like other flags. > > Reviewed-by: Anshuman Khandual Thanks for the reviews! I'll send a patch to document the flag in the near future. - Frank