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V" Subject: Re: [PATCH] hugetlb: Fix __prep_compound_gigantic_page page flag setting Message-ID: <20221119144442.2m7rlexa5sva3fxz@tarunpc> References: <20221118195249.178319-1-mike.kravetz@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221118195249.178319-1-mike.kravetz@oracle.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: zovNgPhbs_RWbLQjqEiZrfhAon-2DaGV X-Proofpoint-GUID: hxHUNeIzBgBLMBpQED7wx75BXejaw-Wt X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.895,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-11-18_08,2022-11-18_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 adultscore=0 priorityscore=1501 spamscore=0 mlxscore=0 lowpriorityscore=0 suspectscore=0 impostorscore=0 phishscore=0 clxscore=1011 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2210170000 definitions=main-2211190110 ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1668869121; a=rsa-sha256; cv=none; b=CmXoElwwNqwHieWSV/drdUwU0Lcne9H4yhPMbql25Vxdy0pF7MNz6KXUGuX09geelxy2mS fQFOx9nb4/cU5frj81VAUQL9EdlKblzVtsbJXCkqoyRNMSpesZBemWwBwQRpV/0L2UStb8 i25r+MVvZfz9YlPPiErZbGQl+sXIQi4= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=LXFqMyoT; spf=pass (imf01.hostedemail.com: domain of tsahu@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=tsahu@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668869120; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=PQEvXswIlOW6EZsPf1TxK+jnGhKVBkvKz2u+YdMR/7I=; b=PYdwNC9zVvZKQa8hN/6GIyvhaiSFphlCxaYIOL78XrRfuOrsJ+uVWllMFP5HQFI0khnTYo HtIZ6ntNRE3NCqluuzkc2Ca3d9Wrzv82ggWz2E7s47Tv9gcl/nhQF/LLRisDBtCpa01+vJ 62N9Rjw8/6oZJ74mxNL+kpv2XMo+eV4= X-Stat-Signature: sajyqwf1kn4wjky9fos56tnofni55pxc X-Rspamd-Queue-Id: 992DA4000F Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=LXFqMyoT; spf=pass (imf01.hostedemail.com: domain of tsahu@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=tsahu@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1668869120-535709 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi, Tested it on top of v6.1.0-rc5 with 1G Hugepages on PPC64le radix MMU. Tested-by: Tarun Sahu ~Tarun On Nov 18 2022, Mike Kravetz wrote: > Commit 2b21624fc232 ("hugetlb: freeze allocated pages before creating > hugetlb pages") changed the order page flags were cleared and set in the > head page. It moved the __ClearPageReserved after __SetPageHead. > However, there is a check to make sure __ClearPageReserved is never > done on a head page. If CONFIG_DEBUG_VM_PGFLAGS is enabled, the > following BUG will be hit when creating a hugetlb gigantic page: > > page dumped because: VM_BUG_ON_PAGE(1 && PageCompound(page)) > ------------[ cut here ]------------ > kernel BUG at include/linux/page-flags.h:500! > Call Trace will differ depending on whether hugetlb page is created > at boot time or run time. > > Make sure to __ClearPageReserved BEFORE __SetPageHead. > > Reported-by: Aneesh Kumar K.V > Fixes: 2b21624fc232 ("hugetlb: freeze allocated pages before creating hugetlb pages") > Signed-off-by: Mike Kravetz > --- > mm/hugetlb.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index e48f8ef45b17..f1385c3b6c96 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -1800,6 +1800,7 @@ static bool __prep_compound_gigantic_page(struct page *page, unsigned int order, > > /* we rely on prep_new_huge_page to set the destructor */ > set_compound_order(page, order); > + __ClearPageReserved(page); > __SetPageHead(page); > for (i = 0; i < nr_pages; i++) { > p = nth_page(page, i); > @@ -1816,7 +1817,8 @@ static bool __prep_compound_gigantic_page(struct page *page, unsigned int order, > * on the head page when they need know if put_page() is needed > * after get_user_pages(). > */ > - __ClearPageReserved(p); > + if (i != 0) /* head page cleared above */ > + __ClearPageReserved(p); > /* > * Subtle and very unlikely > * > -- > 2.38.1 >