From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B7D05F9D0D3 for ; Tue, 14 Apr 2026 15:43:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 085C06B0089; Tue, 14 Apr 2026 11:43:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 00FA16B0092; Tue, 14 Apr 2026 11:43:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E1A4C6B0095; Tue, 14 Apr 2026 11:43:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id CD2F96B0089 for ; Tue, 14 Apr 2026 11:43:30 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 619CE160172 for ; Tue, 14 Apr 2026 15:43:30 +0000 (UTC) X-FDA: 84657580980.26.95EDB27 Received: from out-173.mta0.migadu.com (out-173.mta0.migadu.com [91.218.175.173]) by imf17.hostedemail.com (Postfix) with ESMTP id 0051E40014 for ; Tue, 14 Apr 2026 15:43:26 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="a+Zoy3/H"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf17.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.173 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1776181407; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=xofRIGZTZWakFR4r7hnHb6VQphFQ4wt9gOLnTsomTno=; b=S+OB5GW08w2xDBsrzAavUPJsZW0cP69zj/I+2nL7I8DGSfCdPxH2ctvbqQ39bjhIjE0yPj GAyuJqUMp9EXLcBgSQS1Fda44O8CFJHSbpO6K4+gY10stm5/VTFCXQMrPyCQJoE1GeNkkc FmfLi50eoEAF/ivTdFtuAb7czArdsE4= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776181407; a=rsa-sha256; cv=none; b=z9OYqfwDUvr6kjaBkVDrnmhOmuTTFSdgQEpJ7es/ZzMizVSpSfnntUrglYw6+ist+SNTQh P0PAObJ30JbvtSL2X5NctnAJVPAA09bG+3ERUHghSJ6O/JxKmQ83VicZ98gOhHPHkquIls tnM1xYdd2u9XLIT9J/2glah7ra1Q/wg= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="a+Zoy3/H"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf17.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.173 as permitted sender) smtp.mailfrom=lance.yang@linux.dev X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1776181404; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xofRIGZTZWakFR4r7hnHb6VQphFQ4wt9gOLnTsomTno=; b=a+Zoy3/HP0If3I2KC+z/xy+o4Zd3PZ4Kc0jqpMBHxJwT2FNA1df/rmFfyx81rcasSH+5Hv 3D8TW/roWmTFaZKQaN7FwnaCG0eCBFeUrBT5hmsEqIkTCywMek5EgN3BWqJqRa7+KXE8dh ISMIBMFQ06zz7nJpwbC5FH7qif4qJk0= From: Lance Yang To: ziy@nvidia.com, david@kernel.org Cc: willy@infradead.org, songliubraving@fb.com, clm@fb.com, dsterba@suse.com, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, akpm@linux-foundation.org, ljs@kernel.org, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Lance Yang Subject: Re: [PATCH 7.2 v2 01/12] mm/khugepaged: remove READ_ONLY_THP_FOR_FS check Date: Tue, 14 Apr 2026 23:43:16 +0800 Message-Id: <20260414154316.42935-1-lance.yang@linux.dev> In-Reply-To: <20260414153724.35950-1-lance.yang@linux.dev> References: <20260414153724.35950-1-lance.yang@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 0051E40014 X-Stat-Signature: d8gn8n7g3c611hd771i5zq85ttakcngm X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1776181406-878093 X-HE-Meta: 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 16VCWjmE o+9OmFojjB82KMNMbMmBkz6i33W14vI37ARSt7wWhdbtle3gyRch/mNCtbqQtI/g/JSDMA1RYDXQLvAUHjBVCK6/NcYMwuPXZ01RYk+nkJIXmJgotYQ6D2t84otNdMeMIhp9662+0zqRVZlV3BV4L5BaWIc7aTl0Thw+ETdsDfwk3CTHXWYkMiMomhHh7VWeY6Ix00QwSxfjW+dfnNhLxvDygM877YVnUGVQVjHaxDKzkWakjIr0bVx3gOswbFX6Y/LZn6StyXeYyppgFXneGByNoRGDG2AEkab4l50EaF3VrM1s= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Apr 14, 2026 at 11:37:24PM +0800, Lance Yang wrote: > >On Tue, Apr 14, 2026 at 12:29:04PM +0200, David Hildenbrand (Arm) wrote: >>On 4/13/26 21:20, Zi Yan wrote: >>> collapse_file() requires FSes supporting large folio with at least >>> PMD_ORDER, so replace the READ_ONLY_THP_FOR_FS check with that. >>> MADV_COLLAPSE ignores shmem huge config, so exclude the check for shmem. >>> >>> While at it, replace VM_BUG_ON with VM_WARN_ON_ONCE. >>> >>> In collapse_scan_file(), add FS eligibility check to avoid redundant scans. >>> >>> Signed-off-by: Zi Yan >>> --- >>> mm/khugepaged.c | 12 ++++++++++-- >>> 1 file changed, 10 insertions(+), 2 deletions(-) >>> >>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >>> index b8452dbdb043..d2f0acd2dac2 100644 >>> --- a/mm/khugepaged.c >>> +++ b/mm/khugepaged.c >>> @@ -1892,8 +1892,9 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, >>> int nr_none = 0; >>> bool is_shmem = shmem_file(file); >>> >>> - VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); >>> - VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); >>> + /* MADV_COLLAPSE ignores shmem huge config, so do not check shmem */ >>> + VM_WARN_ON_ONCE(!is_shmem && mapping_max_folio_order(mapping) < PMD_ORDER); >>> + VM_WARN_ON_ONCE(start & (HPAGE_PMD_NR - 1)); >>> >>> result = alloc_charge_folio(&new_folio, mm, cc); >>> if (result != SCAN_SUCCEED) >>> @@ -2321,6 +2322,13 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, >>> int node = NUMA_NO_NODE; >>> enum scan_result result = SCAN_SUCCEED; >>> >>> + /* >>> + * skip files without PMD-order folio support >>> + * do not check shmem, since MADV_COLLAPSE ignores shmem huge config >>> + */ >> >>How is the !collapse path handled? Through thp_vma_allowable_order() in >>collapse_scan_mm_slot()? >> >>Wouldn't it be better to have that check exactly there? > >Right! Looks like patch #03[1] already does that, as David also pointed >out there :) > >With that in place, regular files should end up in file_thp_enabled(), >which checks that mapping_max_folio_order() >= PMD_ORDER. Forgot to add: thp_vma_allowable_order() -> file_thp_enabled() -> mapping_max_folio_order() check >For khugepaged, collapse_scan_mm_slot() calls thp_vma_allowable_order() >before entering the per-PMD scan loop, so ineligible regular file VMAs >should already get filtered there. > >madvise_collapse() also calls thp_vma_allowable_order() early, so it >should get the same filtering before reaching collapse_scan_file(). > >So the extra check here looks redundant :) > >[1] https://lore.kernel.org/linux-mm/20260413192030.3275825-4-ziy@nvidia.com/ > >Cheers, >Lance >