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 94B1EF9D0D5 for ; Tue, 14 Apr 2026 15:37:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 07DBC6B0095; Tue, 14 Apr 2026 11:37:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 054FB6B0096; Tue, 14 Apr 2026 11:37:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ED4156B0098; Tue, 14 Apr 2026 11:37:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id DF9736B0095 for ; Tue, 14 Apr 2026 11:37:39 -0400 (EDT) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id AAE2C1A011B for ; Tue, 14 Apr 2026 15:37:39 +0000 (UTC) X-FDA: 84657566238.15.1E8BDDF Received: from out-177.mta0.migadu.com (out-177.mta0.migadu.com [91.218.175.177]) by imf24.hostedemail.com (Postfix) with ESMTP id B7D87180008 for ; Tue, 14 Apr 2026 15:37:37 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=lAGKQfzg; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf24.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.177 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776181058; a=rsa-sha256; cv=none; b=adLMaDmewQwwRi1Kj2Md7r8m3HC4sFnYyxWgdwGRoyMrJjEamo2HnMuweTF5KqUhQfpM+N QQzwHhWXE1s/FZhDvYXy1dp3JwS9LNjrAwi2o2BZO8b64q09NjUhEjJyOOyW1WLcX9FHLz 2mwJkVsgyCQLu0Bxuelqzn0gcXaONAY= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=lAGKQfzg; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf24.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.177 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=1776181058; 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=m1TDAGgzmOk8H25UKOcIJUxhIEuJydpP4AYeIgjDbV4=; b=vHfF4lstkQdYLgzrpw64X7/x/4o65hu3ae6w7IgqDzDio6gYhq15E7U7KfaeUcZYXak7h/ 633deMsUjAAadFYJgrcTJmxfnUva3M70tbb3rudADvrB7SayD20jz4BweLWv0+Sf65xj9w jctf2Szm8wH3fZzeXowl9ckJMY0P95E= 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=1776181055; 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=m1TDAGgzmOk8H25UKOcIJUxhIEuJydpP4AYeIgjDbV4=; b=lAGKQfzgeioiew63mH3E5n+R9eC1bKNYhY1BlrajddJgdTLtmQ+SiAx0mv0jnamulB/1aj fBWttHSarXPes6jFjVQVGNOlcwl6F2y26bDpQGPgdg4yq9BE7BsqWIynXleZNk8qemiG46 L1j3NTnooylL4ejFk0HNXT7EkZrFaAU= From: Lance Yang To: david@kernel.org, ziy@nvidia.com 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, lance.yang@linux.dev, 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 Subject: Re: [PATCH 7.2 v2 01/12] mm/khugepaged: remove READ_ONLY_THP_FOR_FS check Date: Tue, 14 Apr 2026 23:37:24 +0800 Message-Id: <20260414153724.35950-1-lance.yang@linux.dev> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: kr7ctczmi4pzez1zqjjhqohskh5xtjey X-Rspamd-Queue-Id: B7D87180008 X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1776181057-718348 X-HE-Meta: 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 d8MLmQNG +pa5f4B9U7Mn20Vou0UVY4KJcNhsUZyElEq9XHip9SdyI5CdOCldfU1+PA8CuLxPbL/brl+18PIMaByWI6vKpxEKUCBLCIPsP2rue5k6aBsTpe1e0bGDuU/2cGM1Qho0+wTQsYnplCG4ImYx749kIb4vU4EF6mDjBKoSIoDkTeO0giSeFRHRc9nMoRvFTwkc05FJ9oWscRwP2S6mJnP58qL+GHlXLpmy/ulKIyruQug4cX8zYOkETiteOVZKSF+TtxJ8hcSQM8yBDaKFndX7Kth9gSdAxMlvnDglFkj/L7XJ3xyk= 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 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. 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