On Wed, Nov 04, 2020 at 07:02:20PM +0100, Vlastimil Babka wrote: > On 11/3/20 5:20 PM, Mike Rapoport wrote: > > From: Mike Rapoport <rppt@xxxxxxxxxxxxx> > > Subject should have "on DEBUG_PAGEALLOC" ? > > > The design of DEBUG_PAGEALLOC presumes that __kernel_map_pages() must never > > fail. With this assumption is wouldn't be safe to allow general usage of > > this function. > > > > Moreover, some architectures that implement __kernel_map_pages() have this > > function guarded by #ifdef DEBUG_PAGEALLOC and some refuse to map/unmap > > pages when page allocation debugging is disabled at runtime. > > > > As all the users of __kernel_map_pages() were converted to use > > debug_pagealloc_map_pages() it is safe to make it available only when > > DEBUG_PAGEALLOC is set. > > > > Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> > > Acked-by: David Hildenbrand <david@xxxxxxxxxx> > > Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > --- > > arch/Kconfig | 3 +++ > > arch/arm64/Kconfig | 4 +--- > > arch/arm64/mm/pageattr.c | 8 ++++++-- > > arch/powerpc/Kconfig | 5 +---- > > arch/riscv/Kconfig | 4 +--- > > arch/riscv/include/asm/pgtable.h | 2 -- > > arch/riscv/mm/pageattr.c | 2 ++ > > arch/s390/Kconfig | 4 +--- > > arch/sparc/Kconfig | 4 +--- > > arch/x86/Kconfig | 4 +--- > > arch/x86/mm/pat/set_memory.c | 2 ++ > > include/linux/mm.h | 10 +++++++--- > > 12 files changed, 26 insertions(+), 26 deletions(-) > > > > diff --git a/arch/Kconfig b/arch/Kconfig > > index 56b6ccc0e32d..56d4752b6db6 100644 > > --- a/arch/Kconfig > > +++ b/arch/Kconfig > > @@ -1028,6 +1028,9 @@ config HAVE_STATIC_CALL_INLINE > > bool > > depends on HAVE_STATIC_CALL > > +config ARCH_SUPPORTS_DEBUG_PAGEALLOC > > + bool > > + > > source "kernel/gcov/Kconfig" > > source "scripts/gcc-plugins/Kconfig" > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > index 1d466addb078..a932810cfd90 100644 > > --- a/arch/arm64/Kconfig > > +++ b/arch/arm64/Kconfig > > @@ -71,6 +71,7 @@ config ARM64 > > select ARCH_USE_QUEUED_RWLOCKS > > select ARCH_USE_QUEUED_SPINLOCKS > > select ARCH_USE_SYM_ANNOTATIONS > > + select ARCH_SUPPORTS_DEBUG_PAGEALLOC > > select ARCH_SUPPORTS_MEMORY_FAILURE > > select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK > > select ARCH_SUPPORTS_ATOMIC_RMW > > @@ -1025,9 +1026,6 @@ config HOLES_IN_ZONE > > source "kernel/Kconfig.hz" > > -config ARCH_SUPPORTS_DEBUG_PAGEALLOC > > - def_bool y > > - > > config ARCH_SPARSEMEM_ENABLE > > def_bool y > > select SPARSEMEM_VMEMMAP_ENABLE > > diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c > > index 1b94f5b82654..439325532be1 100644 > > --- a/arch/arm64/mm/pageattr.c > > +++ b/arch/arm64/mm/pageattr.c > > @@ -155,7 +155,7 @@ int set_direct_map_invalid_noflush(struct page *page) > > .clear_mask = __pgprot(PTE_VALID), > > }; > > - if (!rodata_full) > > + if (!debug_pagealloc_enabled() && !rodata_full) > > return 0; > > return apply_to_page_range(&init_mm, > > @@ -170,7 +170,7 @@ int set_direct_map_default_noflush(struct page *page) > > .clear_mask = __pgprot(PTE_RDONLY), > > }; > > - if (!rodata_full) > > + if (!debug_pagealloc_enabled() && !rodata_full) > > return 0; > > return apply_to_page_range(&init_mm, > > I don't understand these two hunks. Previous patch calls this for > hibernation when CONFIG_ARCH_HAS_SET_DIRECT_MAP, which is true for arm64. > Why suddenly this starts to depend on debug_pagealloc_enabled()? I was confused about this for quite a long :) On arm64 the changes to direct^w linear map are allowed when debug_page_alloc() || rodata_full In hibernation we essentially have now if (1) set_direct_map(something) else debug_page_alloc_map() With debug_pagealloc enabled but with rodata_full disabled arm64 versions of set_direct_map_*() will become a nop, so a page that was unmapped by debug_pagealloc() will not be mapped back. I'm still puzzled how hibernation might ever need to save a free page, but that's another story. -- Sincerely yours, Mike.
