From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta0.migadu.com (out-180.mta0.migadu.com [91.218.175.180]) (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 4C118285C91 for ; Sat, 11 Apr 2026 04:00:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775880043; cv=none; b=SDCtZcR93dYQaaxZVyKOT5qPg7y6L9fWVbrQsDpQitwOxzid6x2vM7w5VFVlN5Zb+XJEjW3LSfYnoSUNdjAo9P4OM4XyTvUzfRQk7L1kR2qZ9hrvuYGt+EUAfMaq3ZrmtbmfHKyVFsnc0l/9QIMtEWO3XVWpuQzEQeWa29N8GcM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775880043; c=relaxed/simple; bh=p3GLhe7Q6xMPFNHYVqhydIDivdJGqeDyS1KKwRe66Jg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HbPz/OBTe0vpbm9NLHJY8RHQ+yejhf+35OrZwYThk1TGwiHz6M5f0mgQYG85YZWMvGIohnssvEYrNTXCO5C0DQ0eOxjHAjDcXNeI3ULgSQktvh2bytKJOuMijXjGUBz9JodyU3HHQgHZjHwculDgRnNKQozxLwnWC+9JIIQxszM= 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=PhUoAwrU; arc=none smtp.client-ip=91.218.175.180 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="PhUoAwrU" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1775880039; 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=EK+tj6IXoU9NqDFl67wx0QrRHyI4Qa1XXPET3QHX/dM=; b=PhUoAwrURUEhd79eWEeMZzWool747Xc7qWTtIKl+xSN5Bl/pwAUlWHqlVwpITIj0GCVDHo q9hOt4bOszfYsB03DynzaoHgEADtI6RtkGx7kNtktjRiv+tpBK3e4e16YjbxHQU9C8O/MR 0GOEhfKRtFmwTiiZJiRKy3fqeJ+W2eI= Date: Sat, 11 Apr 2026 12:00:31 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v3 06/10] mm: shmem: drop has_transparent_hugepage() usage Content-Language: en-US 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 References: <020a4fe05e8ac52ca47c27b0fbb6a07c163a118f.1775679721.git.luizcap@redhat.com> <20260410155949.61736-1-lance.yang@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <20260410155949.61736-1-lance.yang@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2026/4/10 23:59, Lance Yang wrote: > > 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 Forgot to add: 4) the buffered write path also falls back for tmpfs mounts > > Nothing jumped out at me, thanks! > > Reviewed-by: Lance Yang