On Wed, Jun 12, 2019 at 2:52 PM Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > > On Wed, Jun 12, 2019 at 2:47 PM Qian Cai <cai@xxxxxx> wrote: > > > > On Wed, 2019-06-12 at 12:38 -0700, Dan Williams wrote: > > > On Wed, Jun 12, 2019 at 12:37 PM Dan Williams <dan.j.williams@xxxxxxxxx> > > > wrote: > > > > > > > > On Wed, Jun 12, 2019 at 12:16 PM Qian Cai <cai@xxxxxx> wrote: > > > > > > > > > > The linux-next commit "mm/sparsemem: Add helpers track active portions > > > > > of a section at boot" [1] causes a crash below when the first kmemleak > > > > > scan kthread kicks in. This is because kmemleak_scan() calls > > > > > pfn_to_online_page(() which calls pfn_valid_within() instead of > > > > > pfn_valid() on x86 due to CONFIG_HOLES_IN_ZONE=n. > > > > > > > > > > The commit [1] did add an additional check of pfn_section_valid() in > > > > > pfn_valid(), but forgot to add it in the above code path. > > > > > > > > > > page:ffffea0002748000 is uninitialized and poisoned > > > > > raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff > > > > > raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff > > > > > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > > > > > ------------[ cut here ]------------ > > > > > kernel BUG at include/linux/mm.h:1084! > > > > > invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI > > > > > CPU: 5 PID: 332 Comm: kmemleak Not tainted 5.2.0-rc4-next-20190612+ #6 > > > > > Hardware name: Lenovo ThinkSystem SR530 -[7X07RCZ000]-/-[7X07RCZ000]-, > > > > > BIOS -[TEE113T-1.00]- 07/07/2017 > > > > > RIP: 0010:kmemleak_scan+0x6df/0xad0 > > > > > Call Trace: > > > > > kmemleak_scan_thread+0x9f/0xc7 > > > > > kthread+0x1d2/0x1f0 > > > > > ret_from_fork+0x35/0x4 > > > > > > > > > > [1] https://patchwork.kernel.org/patch/10977957/ > > > > > > > > > > Signed-off-by: Qian Cai <cai@xxxxxx> > > > > > --- > > > > > include/linux/memory_hotplug.h | 1 + > > > > > 1 file changed, 1 insertion(+) > > > > > > > > > > diff --git a/include/linux/memory_hotplug.h > > > > > b/include/linux/memory_hotplug.h > > > > > index 0b8a5e5ef2da..f02be86077e3 100644 > > > > > --- a/include/linux/memory_hotplug.h > > > > > +++ b/include/linux/memory_hotplug.h > > > > > @@ -28,6 +28,7 @@ > > > > > unsigned long ___nr = pfn_to_section_nr(___pfn); \ > > > > > \ > > > > > if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr) && \ > > > > > + pfn_section_valid(__nr_to_section(___nr), pfn) && \ > > > > > pfn_valid_within(___pfn)) \ > > > > > ___page = pfn_to_page(___pfn); \ > > > > > ___page; \ > > > > > > > > Looks ok to me: > > > > > > > > Acked-by: Dan Williams <dan.j.williams@xxxxxxxxx> > > > > > > > > ...but why is pfn_to_online_page() a multi-line macro instead of a > > > > static inline like all the helper routines it invokes? > > > > > > I do need to send out a refreshed version of the sub-section patchset, > > > so I'll fold this in and give you a Reported-by credit. > > > > BTW, not sure if your new version will fix those two problem below due to the > > same commit. > > > > https://patchwork.kernel.org/patch/10977957/ > > > > 1) offline is busted [1]. It looks like test_pages_in_a_zone() missed the same > > pfn_section_valid() check. > > > > 2) powerpc booting is generating endless warnings [2]. In vmemmap_populated() at > > arch/powerpc/mm/init_64.c, I tried to change PAGES_PER_SECTION to > > PAGES_PER_SUBSECTION, but it alone seems not enough. > > Yes, I was just sending you another note about this. I don't think > your proposed fix is sufficient. The original intent of > pfn_valid_within() was to use it as a cheaper lookup after already > validating that the first page in a MAX_ORDER_NR_PAGES range satisfied > pfn_valid(). Quoting commit 14e072984179 "add pfn_valid_within helper > for sub-MAX_ORDER hole detection": > > Add a pfn_valid_within() helper which should be used when scanning pages > within a MAX_ORDER_NR_PAGES block when we have already checked the > validility > of the block normally with pfn_valid(). This can then be > optimised away when > we do not have holes within a MAX_ORDER_NR_PAGES block of pages. > > So, with that insight I think the complete fix is this: > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 6dd52d544857..9d15ec793330 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1428,7 +1428,7 @@ void memory_present(int nid, unsigned long > start, unsigned long end); > #ifdef CONFIG_HOLES_IN_ZONE > #define pfn_valid_within(pfn) pfn_valid(pfn) > #else > -#define pfn_valid_within(pfn) (1) > +#define pfn_valid_within(pfn) pfn_section_valid(pfn) Well, obviously that won't work because pfn_section_valid needs a 'struct mem_section *' arg, but this does serve as a good check of whether call sites were properly using pfn_valid_within() to constrain the validity after an existing pfn_valid() check within the same MAX_ORDER_NR_PAGES span.
