On Sun, 2020-10-25 at 12:15 +0200, Mike Rapoport wrote: > From: Mike Rapoport <r...@linux.ibm.com> > > When DEBUG_PAGEALLOC or ARCH_HAS_SET_DIRECT_MAP is enabled a page may > be > not present in the direct map and has to be explicitly mapped before > it > could be copied. > > On arm64 it is possible that a page would be removed from the direct > map > using set_direct_map_invalid_noflush() but __kernel_map_pages() will > refuse > to map this page back if DEBUG_PAGEALLOC is disabled.
It looks to me that arm64 __kernel_map_pages() will still attempt to map it if rodata_full is true, how does this happen? > Explicitly use set_direct_map_{default,invalid}_noflush() for > ARCH_HAS_SET_DIRECT_MAP case and debug_pagealloc_map_pages() for > DEBUG_PAGEALLOC case. > > While on that, rename kernel_map_pages() to hibernate_map_page() and > drop > numpages parameter. > > Signed-off-by: Mike Rapoport <r...@linux.ibm.com> > --- > kernel/power/snapshot.c | 29 +++++++++++++++++++---------- > 1 file changed, 19 insertions(+), 10 deletions(-) > > diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c > index fa499466f645..ecb7b32ce77c 100644 > --- a/kernel/power/snapshot.c > +++ b/kernel/power/snapshot.c > @@ -76,16 +76,25 @@ static inline void > hibernate_restore_protect_page(void *page_address) {} > static inline void hibernate_restore_unprotect_page(void > *page_address) {} > #endif /* CONFIG_STRICT_KERNEL_RWX && CONFIG_ARCH_HAS_SET_MEMORY */ > > -#if defined(CONFIG_DEBUG_PAGEALLOC) || > defined(CONFIG_ARCH_HAS_SET_DIRECT_MAP) > -static inline void > -kernel_map_pages(struct page *page, int numpages, int enable) > +static inline void hibernate_map_page(struct page *page, int enable) > { > - __kernel_map_pages(page, numpages, enable); > + if (IS_ENABLED(CONFIG_ARCH_HAS_SET_DIRECT_MAP)) { > + unsigned long addr = (unsigned long)page_address(page); > + int ret; > + > + if (enable) > + ret = set_direct_map_default_noflush(page); > + else > + ret = set_direct_map_invalid_noflush(page); > + > + if (WARN_ON(ret)) > + return; > + > + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); > + } else { > + debug_pagealloc_map_pages(page, 1, enable); > + } > } > -#else > -static inline void > -kernel_map_pages(struct page *page, int numpages, int enable) {} > -#endif > > static int swsusp_page_is_free(struct page *); > static void swsusp_set_page_forbidden(struct page *); > @@ -1366,9 +1375,9 @@ static void safe_copy_page(void *dst, struct > page *s_page) > if (kernel_page_present(s_page)) { > do_copy_page(dst, page_address(s_page)); > } else { > - kernel_map_pages(s_page, 1, 1); > + hibernate_map_page(s_page, 1); > do_copy_page(dst, page_address(s_page)); > - kernel_map_pages(s_page, 1, 0); > + hibernate_map_page(s_page, 0); > } > } > If somehow a page was unmapped such that set_direct_map_default_noflush() would fail, then this code introduces a WARN, but it will still try to read the unmapped page. Why not just have the WARN's inside of __kernel_map_pages() if they fail and then have a warning for the debug page alloc cases as well? Since logic around both expects them not to fail.