From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F1F29D27E; Fri, 30 May 2025 01:58:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748570308; cv=none; b=C54O8MPtY953OgiRVSc6yUj+Mxio21vnMzozUB4HRKMWEqR7fmqJFN6zuHUFV6h2qrUwFWWs8H84VqMjoDA6IG9bFaMNWj2Uu73Qv0pIucT0O5tQmlTMeEeKpkxNjFqIXstJyr8o/cDay7QjvWgIqujbknC8dFdnzREDP9n/zRo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748570308; c=relaxed/simple; bh=jK356KX3q69ZTJwEnZiU9rbuhIM3Iq5jJ2lLNkTH0pE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=DYGpeQoemufmw5CFeKi37fmGTFX3RRRSw6Qvad8cuB2KEyaxMG79vHZa6DzYYW8uC777sLZvuwnox0rHhSspkGuYm/HvBEPSN4mvRzIGAwTi0N0y5ZF7837dgncriKO8N+BVHohOJI58k+VcmvLRnJwHDxcKKxJEZ1CDDk2rnbI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=deRJ4ye6; arc=none smtp.client-ip=115.124.30.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="deRJ4ye6" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1748570296; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=yy5/fgwWGRWQFc3zPba+l8G/Wl8NsYpv5LjubYSD8qY=; b=deRJ4ye6ZSCP0Tobl9QmAF9gKpT4GVrfF7YMM8C0KJsBXSbkVHcyMeDZRIp9beCLx/9vy+GfKjMlPP0RzGuNa1AXJmKXIlU6vjKjJP0xGq9Ef6JIDe5SeMhPl/k5W432HcpCqxb5hMkmo8r96UXgzSTEGvSSAfemtksHbV481G0= Received: from 30.74.144.115(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WcJNvj6_1748570294 cluster:ay36) by smtp.aliyun-inc.com; Fri, 30 May 2025 09:58:15 +0800 Message-ID: Date: Fri, 30 May 2025 09:58:13 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] mm: shmem: disallow hugepages if the system-wide shmem THP sysfs settings are disabled To: Zi Yan Cc: akpm@linux-foundation.org, hughd@google.com, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/5/29 23:21, Zi Yan wrote: > On 29 May 2025, at 4:23, Baolin Wang wrote: > >> The MADV_COLLAPSE will ignore the system-wide shmem THP sysfs settings, which >> means that even though we have disabled the shmem THP configuration, MADV_COLLAPSE >> will still attempt to collapse into a shmem THP. This violates the rule we have >> agreed upon: never means never. >> >> Then the current strategy is: >> For shmem, if none of always, madvise, within_size, and inherit have enabled >> PMD-sized mTHP, then MADV_COLLAPSE will be prohibited from collapsing PMD-sized mTHP. >> >> For tmpfs, if the mount option is set with the 'huge=never' parameter, then >> MADV_COLLAPSE will be prohibited from collapsing PMD-sized mTHP. >> >> Signed-off-by: Baolin Wang >> --- >> mm/huge_memory.c | 2 +- >> mm/shmem.c | 12 ++++++------ >> 2 files changed, 7 insertions(+), 7 deletions(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index d3e66136e41a..a8cfa37cae72 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -166,7 +166,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, >> * own flags. >> */ >> if (!in_pf && shmem_file(vma->vm_file)) >> - return shmem_allowable_huge_orders(file_inode(vma->vm_file), >> + return orders & shmem_allowable_huge_orders(file_inode(vma->vm_file), >> vma, vma->vm_pgoff, 0, >> !enforce_sysfs); > > OK, here orders is checked against allowed orders. > >> >> diff --git a/mm/shmem.c b/mm/shmem.c >> index 4b42419ce6b2..4dbb28d85cd9 100644 >> --- a/mm/shmem.c >> +++ b/mm/shmem.c >> @@ -613,7 +613,7 @@ static unsigned int shmem_get_orders_within_size(struct inode *inode, >> } >> >> static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index, >> - loff_t write_end, bool shmem_huge_force, >> + loff_t write_end, >> struct vm_area_struct *vma, >> unsigned long vm_flags) >> { >> @@ -625,7 +625,7 @@ static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index >> return 0; >> if (shmem_huge == SHMEM_HUGE_DENY) >> return 0; >> - if (shmem_huge_force || shmem_huge == SHMEM_HUGE_FORCE) >> + if (shmem_huge == SHMEM_HUGE_FORCE) >> return maybe_pmd_order; > > shmem_huge is set by sysfs? Yes, through the '/sys/kernel/mm/transparent_hugepage/shmem_enabled' interface. >> /* >> @@ -860,7 +860,7 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo, >> } >> >> static unsigned int shmem_huge_global_enabled(struct inode *inode, pgoff_t index, >> - loff_t write_end, bool shmem_huge_force, >> + loff_t write_end, >> struct vm_area_struct *vma, >> unsigned long vm_flags) >> { >> @@ -1261,7 +1261,7 @@ static int shmem_getattr(struct mnt_idmap *idmap, >> STATX_ATTR_NODUMP); >> generic_fillattr(idmap, request_mask, inode, stat); >> >> - if (shmem_huge_global_enabled(inode, 0, 0, false, NULL, 0)) >> + if (shmem_huge_global_enabled(inode, 0, 0, NULL, 0)) >> stat->blksize = HPAGE_PMD_SIZE; >> >> if (request_mask & STATX_BTIME) { >> @@ -1768,7 +1768,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, >> return 0; >> >> global_orders = shmem_huge_global_enabled(inode, index, write_end, >> - shmem_huge_force, vma, vm_flags); >> + vma, vm_flags); >> /* Tmpfs huge pages allocation */ >> if (!vma || !vma_is_anon_shmem(vma)) >> return global_orders; >> @@ -1790,7 +1790,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, >> /* Allow mTHP that will be fully within i_size. */ >> mask |= shmem_get_orders_within_size(inode, within_size_orders, index, 0); >> >> - if (vm_flags & VM_HUGEPAGE) >> + if (shmem_huge_force || (vm_flags & VM_HUGEPAGE)) >> mask |= READ_ONCE(huge_shmem_orders_madvise); >> >> if (global_orders > 0) >> -- >> 2.43.5 > > shmem_huge_force comes from !enforce_sysfs in __thp_vma_allowable_orders(). > Do you know when sysfs is not enforced and why? IIUC, shmem_huge_force will only be set during MADV_COLLAPSE. Originally, MADV_COLLAPSE was intended to ignore the system-wide THP sysfs settings. However, if all system-wide shmem THP settings are disabled, we should not allow MADV_COLLAPSE to collapse a THP. This is the issue this patchset aims to fix. Thanks for the review.