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 7D8C2FAD3F0 for ; Thu, 23 Apr 2026 02:43:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BC0E96B0005; Wed, 22 Apr 2026 22:43:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B71E96B008A; Wed, 22 Apr 2026 22:43:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A61836B008C; Wed, 22 Apr 2026 22:43:44 -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 93E046B0005 for ; Wed, 22 Apr 2026 22:43:44 -0400 (EDT) Received: from smtpin01.hostedemail.com (lb01b-stub [10.200.18.250]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 235C040251 for ; Thu, 23 Apr 2026 02:43:44 +0000 (UTC) X-FDA: 84688275168.01.8CFDED4 Received: from out-184.mta0.migadu.com (out-184.mta0.migadu.com [91.218.175.184]) by imf19.hostedemail.com (Postfix) with ESMTP id 588931A0015 for ; Thu, 23 Apr 2026 02:43:42 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="dbVPz/70"; spf=pass (imf19.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.184 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1776912222; 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=lMukq5Ux3ezv5Tyfl0FoaOXQcgnvMJcY/OsebFof9qE=; b=aoMSql2gC+Jhq7OOZ9lB/TB29v0/k0LZTYGF5DzM9Anj4l/bksvDe1XnWmY3UNGAQomvJ3 69iW3xReYciTgPAoUAa5cW1wOMMWMlyVyT503j6mCeAlW3N9okdcFbUJXVU+YEfiZXCvNj KzZ97+aZhpIjpoCHY0JyU5wCvNhI6qc= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="dbVPz/70"; spf=pass (imf19.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.184 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776912222; a=rsa-sha256; cv=none; b=x2WpvfaHHC7asRpvNU2GQqc3wr4BohatVL1DHJQjItALn29WBw49iDTuAAAsc2sT78LpKk +OOxrRA1ut4ikIsE4bbitY4zdkgu7mDwXsjdZ47XwT+hBjcUTIJ5Ghxez6uyt5JDYs/PPP jJw5f6RuPwz/KhhIlivkYnDYfKEONFk= 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=1776912219; 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=lMukq5Ux3ezv5Tyfl0FoaOXQcgnvMJcY/OsebFof9qE=; b=dbVPz/70tYHnFMXxFY25JlFErOfD2J4+flnFzZWIC+GFQLAapotxsFxlAWVXDzN/3tqSgp 7ZkBqd9Q4CRT3BAfi8roSgJ3+PwfRM3RTMma7KOb7LXwjYwl89WkYLG6UjTE0BMSSNEtUh o25vpDGVCfCldSri1nd6fxpGOgDUlW8= From: Lance Yang To: 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, david@kernel.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 v3 01/12] mm/khugepaged: remove READ_ONLY_THP_FOR_FS check Date: Thu, 23 Apr 2026 10:43:24 +0800 Message-Id: <20260423024324.51588-1-lance.yang@linux.dev> In-Reply-To: <20260418024429.4055056-2-ziy@nvidia.com> References: <20260418024429.4055056-2-ziy@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 588931A0015 X-Stat-Signature: b1ec5qomxz9nunzej3huxzyf1mfuhyne X-Rspam-User: X-HE-Tag: 1776912222-698035 X-HE-Meta: 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 SeIPo8yO 0Q257023pCoZnlz4Sz9ZT8xM1/NsdiVVDpwTyQDlDyiKObe95rJqsYl6cYKWovIiIJCY7VGVLmr9VlTDZtT2C4IJBxslSdj0Oi3K2uJgMlt5HAvuVID4PzKliC+QEbRfJdL5b0523Vy78SfyZvVVHmIO1uSsHCdiDvSco2zlds3ff2ADzRM/8LvsOecu3YNXLufQlWjKyucOtgaZirFXt1KtfpdQL6gwJ8M8J/w4zoj7ZpTJx8LvhlC3L9Om0vgKW60DSrTCduxNg/9DjOQ52B+RUs0Z49/4UIu7GK4drj1ovNk1DxIBnbUq/mAPDvpwn8x70Ztfn06RUjgiWAoAjNuThCLErbzfPHAGairQyHW0QMYU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 17, 2026 at 10:44:18PM -0400, 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. > >Add a helper function mapping_pmd_thp_support() for FSes supporting large >folio with at least PMD_ORDER. > >Signed-off-by: Zi Yan >--- > include/linux/pagemap.h | 10 ++++++++++ > mm/khugepaged.c | 5 +++-- > 2 files changed, 13 insertions(+), 2 deletions(-) > >diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h >index ec442af3f886..c3cb1ec982cd 100644 >--- a/include/linux/pagemap.h >+++ b/include/linux/pagemap.h >@@ -524,6 +524,16 @@ static inline bool mapping_large_folio_support(const struct address_space *mappi > return mapping_max_folio_order(mapping) > 0; > } > >+static inline bool mapping_pmd_thp_support(const struct address_space *mapping) >+{ >+ /* AS_FOLIO_ORDER is only reasonable for pagecache folios */ >+ VM_WARN_ONCE((unsigned long)mapping & FOLIO_MAPPING_ANON, >+ "Anonymous mapping always supports PMD THP"); Nit: afraid not, at least when running on architectures without PMD leaf entries ... Maybe better to say this helper is only meaningful for pagecache-backed mappings. Anonymous mappings should not reach here. >+ >+ return mapping_max_folio_order(mapping) >= PMD_ORDER; >+} >+ >+ > /* Return the maximum folio size for this pagecache mapping, in bytes. */ > static inline size_t mapping_max_folio_size(const struct address_space *mapping) > { >diff --git a/mm/khugepaged.c b/mm/khugepaged.c >index b8452dbdb043..3eb5d982d3d3 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_pmd_thp_support(mapping)); With [1], can we drop !is_shmem here as well? shmem would then always call mapping_set_large_folios(inode->i_mapping): ---8<--- diff --git a/mm/shmem.c b/mm/shmem.c index 4ecefe02881d..dafbea53b22d 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3087,10 +3087,7 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap, cache_no_acl(inode); if (sbinfo->noswap) mapping_set_unevictable(inode->i_mapping); - - /* Don't consider 'deny' for emergencies and 'force' for testing */ - if (sbinfo->huge) - mapping_set_large_folios(inode->i_mapping); + mapping_set_large_folios(inode->i_mapping); switch (mode & S_IFMT) { default: -- But we can do that in a follow-up, once the revert lands :) [1] https://lore.kernel.org/linux-mm/b2c7deee259a94b0d00a7c320d8d24d2c421f761.1776908112.git.baolin.wang@linux.alibaba.com/