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From: Muchun Song In-Reply-To: Date: Thu, 22 May 2025 15:13:31 +0800 Cc: yangge1116@126.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, 21cnbao@gmail.com, david@redhat.com, baolin.wang@linux.alibaba.com, liuzixing@hygon.cn Content-Transfer-Encoding: quoted-printable Message-Id: <065093C4-3599-456F-84B7-EDCC1A3E8AFC@linux.dev> References: <1747884137-26685-1-git-send-email-yangge1116@126.com> <644FF836-9DC7-42B4-BACE-C433E637B885@linux.dev> To: Oscar Salvador X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 7228C4000A X-Stat-Signature: ap6omfxyoc9ccgeudkk7ys1w37t5b9qf X-Rspam-User: X-HE-Tag: 1747898058-337749 X-HE-Meta: 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 VnrIcuGq XQcQnOpDGp/Ziuae8MisZ7D7jDjikAOHkaFXgoB+5NHozdd2thM/kwdt6YRwcGML6KGHo8usSSPCDnuOKusI1jJ3/dmrxbtEse/uRIywUbeOE7I8GBa5GdZVInhuU9IjPOjuWTYR0FYdPvUJOngjkj7fMBP8Pv1U/8spMctl/ozMTSlGQ3PVFcC7RqmbjxVDruDvaAk4SBiEWhTtyt0C5gy68J3HfuR6dj4BNkjflR54qtIEn0Yod630CZg== 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 May 22, 2025, at 13:34, Oscar Salvador wrote: >=20 > On Thu, May 22, 2025 at 11:47:05AM +0800, Muchun Song wrote: >> Thanks for fixing this problem. BTW, in order to catch future similar = problem, >> it is better to add WARN_ON into folio_hstate() to assert if = hugetlb_lock >> is not held when folio's reference count is zero. For this fix, LGTM. >=20 > Why cannot we put all the burden in = alloc_and_dissolve_hugetlb_folio(), > which will again check things under the lock? I've also considered about this choice, because there is another similar case in isolate_or_dissolve_huge_page() which could benefit from this change. I am fine with both approaches. Anyway, adding an assertion into folio_hstate() is an improvement for capturing invalid users in the = future. Because any user of folio_hstate() should hold a reference to folio or hold the hugetlb_lock to make sure it returns a valid hstate for a = hugetlb folio. Muchun, Thanks. > I mean, I would be ok to save cycles and check upfront in > replace_free_hugepage_folios(), but the latter has only one user which > is alloc_contig_range(), which is not really an expected-to-be = optimized > function. >=20 > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index bd8971388236..b4d937732256 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2924,13 +2924,6 @@ int replace_free_hugepage_folios(unsigned long = start_pfn, unsigned long end_pfn) >=20 > while (start_pfn < end_pfn) { > folio =3D pfn_folio(start_pfn); > - if (folio_test_hugetlb(folio)) { > - h =3D folio_hstate(folio); > - } else { > - start_pfn++; > - continue; > - } > - > if (!folio_ref_count(folio)) { > ret =3D alloc_and_dissolve_hugetlb_folio(h, = folio, > &isolate_list); >=20 >=20 >=20 > --=20 > Oscar Salvador > SUSE Labs