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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Zach O'Keefe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chris Mason , stable@vger.kernel.org Subject: Re: [PATCH] mm/khugepaged: don't map folios that are not uptodate in MADV_COLLAPSE Message-ID: References: <20261105-set_huge_pmd_uptodate-v1-1-a78d8a1b7117@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261105-set_huge_pmd_uptodate-v1-1-a78d8a1b7117@kernel.org> X-Stat-Signature: r6fw54uoo1knb1pw1b55aaihgtzfwpdn X-Rspamd-Queue-Id: C91A714000C X-Rspam-User: X-Rspamd-Server: rspam11 X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793907259-414692 X-HE-Meta: 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 bcrO6i6S 5M5G2hxZFgbeEuTC1miz428HtBf4OqfoYjiYT684bSeBtJ4HRZl8QRI1JObzPGFUgvrksIObTxj5EVuUhDamQPMbKUQK4Qb6yiHk+IBPEciRXldSw9evGG5Nw//73okrCQMWzwaMNXM7VkJdsM7G4zHA3WHWFLq/a/rXH7/Vw7hm3PnJv9TMbiu55/jOwNzSOXpoWoj04kCjBQqCx4s6C3+nq31v89K7qIrlfcuxSbt4O2nbTdiS3/f1MAZrhynHPqptN2p9+fKfT62T1Np1T4pXVeEXVnluD6Hy4ovw5yxfZiktadZq4/S0/SksZ9dG6cyG9 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Nov 05, 2026 at 07:16:44PM +0100, David Hildenbrand (Arm) wrote: > madvise(MADV_COLLAPSE) can map PMD-sized pagecache folios that are not > uptodate. For example, shmem fallocate() can put such folios into the > page cache. > > collapse_file() already refuses to proceed with folios that are not > uptodate. Let's just do the same in try_collapse_pte_mapped_thp() and skip > such folios, leaving handling to the page faults. > > Note that collapse_file() effectively clears shmem folios through > shmem_get_folio(); let's keep this fix simple and simply let the page > fault path deal with that. > > Fixes: 34488399fa08 ("mm/madvise: add file and shmem support to MADV_COLLAPSE") > Reported-by: Chris Mason > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) Looks reasonable to me, there's no reason we should be dealing with non-uptodate folios there. Reviewed-by: Lorenzo Stoakes (ARM) > --- > Once reviewed, I will pick this up in a timely manner. > --- > mm/khugepaged.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 8d9f05a39afb3..db135b3c44ef1 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1900,6 +1900,12 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign > goto drop_folio; > } > > + /* Leave any uninitialized folios to the page fault path. */ > + if (!folio_test_uptodate(folio)) { > + result = SCAN_FAIL; > + goto drop_folio; > + } > + > result = find_pmd_or_thp_or_none(mm, haddr, &pmd); > switch (result) { > case SCAN_SUCCEED: > > --- > > base-commit: f44fd601f72e09e44c667b9234c9cd469856679c > > change-id: 20261105-set_huge_pmd_uptodate-9b9820307f30 > > -- > > Cheers, > > David > -- Cheers, Lorenzo