Re: [PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online_page()

[Qian Cai]

On Wed, 2019-06-12 at 12:37 -0700, Dan Williams 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:
> > Âkmemleak_scan_thread+0x9f/0xc7
> > Âkthread+0x1d2/0x1f0
> > Âret_from_fork+0x35/0x4
> > 
> > [1] https://patchwork.kernel.org/patch/10977957/
> > 
> > Signed-off-by: Qian Cai <cai@xxxxxx>
> > ---
> > Âinclude/linux/memory_hotplug.h | 1 +
> > Â1 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 @@
> > ÂÂÂÂÂÂÂÂunsigned long ___nr = pfn_to_section_nr(___pfn);ÂÂÂÂÂÂÂÂÂÂÂ\
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ\
> > ÂÂÂÂÂÂÂÂif (___nr < NR_MEM_SECTIONS && online_section_nr(___nr) && \
> > +ÂÂÂÂÂÂÂÂÂÂÂpfn_section_valid(__nr_to_section(___nr), pfn) &&ÂÂÂÂÂÂ\
> > ÂÂÂÂÂÂÂÂÂÂÂÂpfn_valid_within(___pfn))ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ\
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ___page = pfn_to_page(___pfn);ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ\
> > ÂÂÂÂÂÂÂÂ___page;ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ\
> 
> 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?

Sigh, probably because it is a mess over there.

memory_hotplug.h and mmzone.h are included each other. Converted it directly to
a static inline triggers compilation errors because mmzone.h was included
somewhere else and found pfn_to_online_page() needs things like
pfn_valid_within() and online_section_nr() etc which are only defined later in
mmzone.h.

Move pfn_to_online_page() into mmzone.h triggers errors below.

In file included from ./arch/x86/include/asm/page.h:76,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂfrom ./arch/x86/include/asm/thread_info.h:12,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂfrom ./include/linux/thread_info.h:38,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂfrom ./arch/x86/include/asm/preempt.h:7,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂfrom ./include/linux/preempt.h:78,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂfrom ./include/linux/spinlock.h:51,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂfrom ./include/linux/mmzone.h:8,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂfrom ./include/linux/gfp.h:6,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂfrom ./include/linux/slab.h:15,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂfrom ./include/linux/crypto.h:19,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂfrom arch/x86/kernel/asm-offsets.c:9:
./include/linux/memory_hotplug.h: In function âpfn_to_online_pageâ:
./include/asm-generic/memory_model.h:54:29: error: âvmemmapâ undeclared (first
use in this function); did you mean âmem_mapâ?
Â#define __pfn_to_page(pfn) (vmemmap + (pfn))
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ^~~~~~~
./include/asm-generic/memory_model.h:82:21: note: in expansion of macro
â__pfn_to_pageâ
Â#define pfn_to_page __pfn_to_page
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ^~~~~~~~~~~~~
./include/linux/memory_hotplug.h:30:10: note: in expansion of macro
âpfn_to_pageâ
ÂÂÂreturn pfn_to_page(pfn);
ÂÂÂÂÂÂÂÂÂÂ^~~~~~~~~~~
./include/asm-generic/memory_model.h:54:29: note: each undeclared identifier is
reported only once for each function it appears in
Â#define __pfn_to_page(pfn) (vmemmap + (pfn))
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ^~~~~~~
./include/asm-generic/memory_model.h:82:21: note: in expansion of macro
â__pfn_to_pageâ
Â#define pfn_to_page __pfn_to_page
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ^~~~~~~~~~~~~
./include/linux/memory_hotplug.h:30:10: note: in expansion of macro
âpfn_to_pageâ
ÂÂÂreturn pfn_to_page(pfn);
ÂÂÂÂÂÂÂÂÂÂ^~~~~~~~~~~
make[1]: *** [scripts/Makefile.build:112: arch/x86/kernel/asm-offsets.s] Error 1