| Message ID | 20221118195249.178319-1-mike.kravetz@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | hugetlb: Fix __prep_compound_gigantic_page page flag setting | expand |
On 2022/11/19 3:52, 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 <aneesh.kumar@linux.ibm.com> > Fixes: 2b21624fc232 ("hugetlb: freeze allocated pages before creating hugetlb pages") > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Yes, PG_reserved is PF_NO_COMPOUND policy. Thanks for fixing this. Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> Thanks, Miaohe Lin
Hi, Tested it on top of v6.1.0-rc5 with 1G Hugepages on PPC64le radix MMU. Tested-by: Tarun Sahu <tsahu@linux.ibm.com> ~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 <aneesh.kumar@linux.ibm.com> > Fixes: 2b21624fc232 ("hugetlb: freeze allocated pages before creating hugetlb pages") > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> > --- > 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 >
> On Nov 19, 2022, at 03:52, Mike Kravetz <mike.kravetz@oracle.com> 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 <aneesh.kumar@linux.ibm.com> > Fixes: 2b21624fc232 ("hugetlb: freeze allocated pages before creating hugetlb pages") > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Acked-by: Muchun Song <songmuchun@bytedance.com> Thanks.
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 *
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 <aneesh.kumar@linux.ibm.com> Fixes: 2b21624fc232 ("hugetlb: freeze allocated pages before creating hugetlb pages") Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> --- mm/hugetlb.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)