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Subject: Re: [PATCH v3 2/4] hugetlbfs: move hugepagesz= parsing to arch
 independent code
From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     Sandipan Das <sandipan.osd@gmail.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
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        linux-doc@vger.kernel.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        "David S.Miller" <davem@davemloft.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Longpeng <longpeng2@huawei.com>,
        Christophe Leroy <christophe.leroy@c-s.fr>,
        Randy Dunlap <rdunlap@infradead.org>,
        Mina Almasry <almasrymina@google.com>,
        Peter Xu <peterx@redhat.com>,
        Nitesh Narayan Lal <nitesh@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>
References: <20200417185049.275845-1-mike.kravetz@oracle.com>
 <20200417185049.275845-3-mike.kravetz@oracle.com>
 <7583dfcc-62d8-2a54-6eef-bcb4e01129b3@gmail.com>
 <5a380060-38db-b690-1003-678ca0f28f07@oracle.com>
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Date:   Mon, 27 Apr 2020 12:09:47 -0700
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On 4/27/20 10:25 AM, Mike Kravetz wrote:
> On 4/26/20 10:04 PM, Sandipan Das wrote:
>> On 18/04/20 12:20 am, Mike Kravetz wrote:
>>> Now that architectures provide arch_hugetlb_valid_size(), parsing
>>> of "hugepagesz=" can be done in architecture independent code.
>>
>> This isn't working as expected on powerpc64.
>>
>>   [    0.000000] Kernel command line: root=UUID=dc7b49cf-95a2-4996-8e7d-7c64ddc7a6ff hugepagesz=16G hugepages=2 
>>   [    0.000000] HugeTLB: huge pages not supported, ignoring hugepagesz = 16G
>>   [    0.000000] HugeTLB: huge pages not supported, ignoring hugepages = 2
>>   [    0.284177] HugeTLB registered 16.0 MiB page size, pre-allocated 0 pages
>>   [    0.284182] HugeTLB registered 16.0 GiB page size, pre-allocated 0 pages
>>   [    2.585062]     hugepagesz=16G
>>   [    2.585063]     hugepages=2
>>
> 
> In the new arch independent version of hugepages_setup, I added the following
> code in patch 4 off this series:
> 
>> +	if (!hugepages_supported()) {
>> +		pr_warn("HugeTLB: huge pages not supported, ignoring hugepages = %s\n", s);
>> +		return 0;
>> +	}
>> +
> 
> The easy solution is to remove all the hugepages_supported() checks from
> command line parsing routines and rely on the later check in hugetlb_init().

Here is a patch to address the issue.  Sorry, as my series breaks all hugetlb
command line processing on powerpc.

Sandipan, can you test the following patch?

From 480fe2847361e2a85aeec1fb39fe643bb7100a07 Mon Sep 17 00:00:00 2001
From: Mike Kravetz <mike.kravetz@oracle.com>
Date: Mon, 27 Apr 2020 11:37:30 -0700
Subject: [PATCH] hugetlbfs: fix changes to command line processing

Previously, a check for hugepages_supported was added before processing
hugetlb command line parameters.  On some architectures such as powerpc,
hugepages_supported() is not set to true until after command line
processing.  Therefore, no hugetlb command line parameters would be
accepted.

Remove the additional checks for hugepages_supported.  In hugetlb_init,
print a warning if !hugepages_supported and command line parameters were
specified.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 mm/hugetlb.c | 20 ++++----------------
 1 file changed, 4 insertions(+), 16 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 1075abdb5717..5548e8851b93 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3212,8 +3212,11 @@ static int __init hugetlb_init(void)
 {
 	int i;
 
-	if (!hugepages_supported())
+	if (!hugepages_supported()) {
+		if (hugetlb_max_hstate || default_hstate_max_huge_pages)
+			pr_warn("HugeTLB: huge pages not supported, ignoring associated command-line parameters\n");
 		return 0;
+	}
 
 	/*
 	 * Make sure HPAGE_SIZE (HUGETLB_PAGE_ORDER) hstate exists.  Some
@@ -3315,11 +3318,6 @@ static int __init hugepages_setup(char *s)
 	unsigned long *mhp;
 	static unsigned long *last_mhp;
 
-	if (!hugepages_supported()) {
-		pr_warn("HugeTLB: huge pages not supported, ignoring hugepages = %s\n", s);
-		return 0;
-	}
-
 	if (!parsed_valid_hugepagesz) {
 		pr_warn("HugeTLB: hugepages=%s does not follow a valid hugepagesz, ignoring\n", s);
 		parsed_valid_hugepagesz = true;
@@ -3372,11 +3370,6 @@ static int __init hugepagesz_setup(char *s)
 	struct hstate *h;
 
 	parsed_valid_hugepagesz = false;
-	if (!hugepages_supported()) {
-		pr_warn("HugeTLB: huge pages not supported, ignoring hugepagesz = %s\n", s);
-		return 0;
-	}
-
 	size = (unsigned long)memparse(s, NULL);
 
 	if (!arch_hugetlb_valid_size(size)) {
@@ -3424,11 +3417,6 @@ static int __init default_hugepagesz_setup(char *s)
 	unsigned long size;
 
 	parsed_valid_hugepagesz = false;
-	if (!hugepages_supported()) {
-		pr_warn("HugeTLB: huge pages not supported, ignoring default_hugepagesz = %s\n", s);
-		return 0;
-	}
-
 	if (parsed_default_hugepagesz) {
 		pr_err("HugeTLB: default_hugepagesz previously specified, ignoring %s\n", s);
 		return 0;
-- 
2.25.4