From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (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 36EB13DA5A6 for ; Fri, 10 Apr 2026 16:00:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775836806; cv=none; b=RlEoIlaRM5SI4KDwMDh0dex2SQjd1/nQm19R9zEfuawlrh7i+wegSN1qrFu8N8af/4bcX6zF36cMCkT9QGyEaIsOUguL1zFDCQbpLnazS1Q5qzwDwE+mtXXcFHCKsfUakj2WFtEiNwIrJrZgMmalFYnvkV4F48ZAzqXIfF3IT9Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775836806; c=relaxed/simple; bh=V9x4mxc3OqRD2mrEBYOml7+kHCtkQzFB1PqjxFWUaRo=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=NWY/YkVCvEuyDvVXPpJtmX+QM8bwaeTN5vQ5ZiXMTkyBn7VsWZ2SbD+VQhJnzJYxZ9P87FJcqs5GRFMikY5ODhtHG67WE3pVJtMzQh0CC5xrPfdvjuiCh5fsBYr5AuOtek63FH9ij/XtyGZqzXD7xDN5lZIfPEIame6smv/jyTA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=lZkU3a2r; arc=none smtp.client-ip=91.218.175.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="lZkU3a2r" 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=1775836800; 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=Fp69nvi8vfzePQ4r72WtQoyz3vGVsf9eWxbGaVqWFg8=; b=lZkU3a2r1eBilnZoCEuBaVnKpRHbeu4XB1hX/wQNN0o6A4IkvYn0CdSgIXL8mvywcuamhI 6Rbl7q36L8b7BREjPmzIk6CWxfiXVXMBV7zYTj0rytk1ezzNfgD130Dayp49686v1a7laI lR75D1TZtW8RtqJP+c8wqS8IamWlH9M= From: Lance Yang To: luizcap@redhat.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, baolin.wang@linux.alibaba.com, ryan.roberts@arm.com, akpm@linux-foundation.org, ljs@kernel.org, ziy@nvidia.com, Liam.Howlett@oracle.com, npache@redhat.com, dev.jain@arm.com, baohua@kernel.org, Lance Yang Subject: Re: [PATCH v3 06/10] mm: shmem: drop has_transparent_hugepage() usage Date: Fri, 10 Apr 2026 23:59:49 +0800 Message-Id: <20260410155949.61736-1-lance.yang@linux.dev> In-Reply-To: <020a4fe05e8ac52ca47c27b0fbb6a07c163a118f.1775679721.git.luizcap@redhat.com> References: <020a4fe05e8ac52ca47c27b0fbb6a07c163a118f.1775679721.git.luizcap@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On Wed, Apr 08, 2026 at 04:23:01PM -0400, Luiz Capitulino wrote: >Shmem uses has_transparent_hugepage() in the following ways: > >- shmem_parse_one() and shmem_parse_huge(): Check if THP is built-in and > if the CPU supports PMD-sized pages > >- shmem_init(): Since the CONFIG_TRANSPARENT_HUGEPAGE guard is outside > the code block calling has_transparent_hugepage(), the > has_transparent_hugepage() call is exclusively checking if the CPU > supports PMD-sized pages > >While it's necessary to check if CONFIG_TRANSPARENT_HUGEPAGE is enabled >in all cases, shmem can determine mTHP size support at folio allocation >time. Therefore, drop has_transparent_hugepage() usage while keeping the >CONFIG_TRANSPARENT_HUGEPAGE checks. > >Signed-off-by: Luiz Capitulino >--- > mm/shmem.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > >diff --git a/mm/shmem.c b/mm/shmem.c >index b40f3cd48961..6f8b20d77e07 100644 >--- a/mm/shmem.c >+++ b/mm/shmem.c >@@ -689,7 +689,7 @@ static int shmem_parse_huge(const char *str) > else > return -EINVAL; > >- if (!has_transparent_hugepage() && >+ if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && > huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY) > return -EINVAL; > >@@ -4664,8 +4664,7 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param) > case Opt_huge: > ctx->huge = result.uint_32; > if (ctx->huge != SHMEM_HUGE_NEVER && >- !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && >- has_transparent_hugepage())) >+ !IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > goto unsupported_parameter; > ctx->seen |= SHMEM_SEEN_HUGE; > break; >@@ -5451,7 +5450,7 @@ void __init shmem_init(void) > #endif > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE >- if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY) >+ if (shmem_huge > SHMEM_HUGE_DENY) > SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge; > else > shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */ >-- Although this patch simply drops the early has_transparent_hugepage() checks from the shmem parse/init paths, shmem_allowable_huge_orders() still returns 0 when thp_disabled_by_hw() is set. So on hardware without PMD THP support: unsigned long shmem_allowable_huge_orders(struct inode *inode, struct vm_area_struct *vma, pgoff_t index, loff_t write_end, bool shmem_huge_force) { ... if (thp_disabled_by_hw() || (vma && vma_thp_disabled(vma, vm_flags, shmem_huge_force))) return 0; ... } 1) the fault path still falls back to order-0 allocation 2) do_set_pmd() still falls back 3) khugepaged won't collapse it either Nothing jumped out at me, thanks! Reviewed-by: Lance Yang