On Tue 13-02-18 14:31:58, Pavel Tatashin wrote: > During boot we poison struct page memory in order to ensure that no one is > accessing this memory until the struct pages are initialized in > __init_single_page(). > > This patch adds more scrutiny to this checking, by making sure that flags > do not equal to poison pattern when the are accessed. The pattern is all
s@the are@they are@ > ones. > > Since, node id is also stored in struct page, and may be accessed quiet s@quiet@quite@ > early we add the enforcement into page_to_nid() function as well. It would be worth adding that this applies only to NODE_NOT_IN_PAGE_FLAGS=n > Signed-off-by: Pavel Tatashin <[email protected]> Other than that it looks like a reasonable debugging feature. Acked-by: Michal Hocko <[email protected]> > --- > include/linux/mm.h | 4 +++- > include/linux/page-flags.h | 22 +++++++++++++++++----- > mm/memblock.c | 2 +- > 3 files changed, 21 insertions(+), 7 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index ad06d42adb1a..ad71136a6494 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -896,7 +896,9 @@ extern int page_to_nid(const struct page *page); > #else > static inline int page_to_nid(const struct page *page) > { > - return (page->flags >> NODES_PGSHIFT) & NODES_MASK; > + struct page *p = (struct page *)page; > + > + return (PF_POISONED_CHECK(p)->flags >> NODES_PGSHIFT) & NODES_MASK; > } > #endif > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 50c2b8786831..5d5493e1f7ba 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -156,9 +156,18 @@ static __always_inline int PageCompound(struct page > *page) > return test_bit(PG_head, &page->flags) || PageTail(page); > } > > +#define PAGE_POISON_PATTERN ~0ul > +static inline int PagePoisoned(const struct page *page) > +{ > + return page->flags == PAGE_POISON_PATTERN; > +} > + > /* > * Page flags policies wrt compound pages > * > + * PF_POISONED_CHECK > + * check if this struct page poisoned/uninitialized > + * > * PF_ANY: > * the page flag is relevant for small, head and tail pages. > * > @@ -176,17 +185,20 @@ static __always_inline int PageCompound(struct page > *page) > * PF_NO_COMPOUND: > * the page flag is not relevant for compound pages. > */ > -#define PF_ANY(page, enforce) page > -#define PF_HEAD(page, enforce) compound_head(page) > +#define PF_POISONED_CHECK(page) ({ \ > + VM_BUG_ON_PGFLAGS(PagePoisoned(page), page); \ > + page;}) > +#define PF_ANY(page, enforce) PF_POISONED_CHECK(page) > +#define PF_HEAD(page, enforce) PF_POISONED_CHECK(compound_head(page)) > #define PF_ONLY_HEAD(page, enforce) ({ > \ > VM_BUG_ON_PGFLAGS(PageTail(page), page); \ > - page;}) > + PF_POISONED_CHECK(page);}) > #define PF_NO_TAIL(page, enforce) ({ \ > VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \ > - compound_head(page);}) > + PF_POISONED_CHECK(compound_head(page));}) > #define PF_NO_COMPOUND(page, enforce) ({ \ > VM_BUG_ON_PGFLAGS(enforce && PageCompound(page), page); \ > - page;}) > + PF_POISONED_CHECK(page);}) > > /* > * Macros to create function definitions for page flags > diff --git a/mm/memblock.c b/mm/memblock.c > index 5a9ca2a1751b..d85c8754e0ce 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -1373,7 +1373,7 @@ void * __init memblock_virt_alloc_try_nid_raw( > min_addr, max_addr, nid); > #ifdef CONFIG_DEBUG_VM > if (ptr && size > 0) > - memset(ptr, 0xff, size); > + memset(ptr, PAGE_POISON_PATTERN, size); > #endif > return ptr; > } > -- > 2.16.1 > -- Michal Hocko SUSE Labs
