On Wed, Dec 12, 2018 at 06:27:12PM +0100, Mikhail Zaslonko wrote: >If memory end is not aligned with the sparse memory section boundary, the >mapping of such a section is only partly initialized. This may lead to >VM_BUG_ON due to uninitialized struct page access from >is_mem_section_removable() or test_pages_in_a_zone() function triggered by >memory_hotplug sysfs handlers: > >Here are the the panic examples: > CONFIG_DEBUG_VM=y > CONFIG_DEBUG_VM_PGFLAGS=y > > kernel parameter mem=2050M > -------------------------- > page:000003d082008000 is uninitialized and poisoned > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > Call Trace: > ([<0000000000385b26>] test_pages_in_a_zone+0xde/0x160) > [<00000000008f15c4>] show_valid_zones+0x5c/0x190 > [<00000000008cf9c4>] dev_attr_show+0x34/0x70 > [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148 > [<00000000003e4194>] seq_read+0x204/0x480 > [<00000000003b53ea>] __vfs_read+0x32/0x178 > [<00000000003b55b2>] vfs_read+0x82/0x138 > [<00000000003b5be2>] ksys_read+0x5a/0xb0 > [<0000000000b86ba0>] system_call+0xdc/0x2d8 > Last Breaking-Event-Address: > [<0000000000385b26>] test_pages_in_a_zone+0xde/0x160 > Kernel panic - not syncing: Fatal exception: panic_on_oops > > kernel parameter mem=3075M > -------------------------- > page:000003d08300c000 is uninitialized and poisoned > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > Call Trace: > ([<000000000038596c>] is_mem_section_removable+0xb4/0x190) > [<00000000008f12fa>] show_mem_removable+0x9a/0xd8 > [<00000000008cf9c4>] dev_attr_show+0x34/0x70 > [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148 > [<00000000003e4194>] seq_read+0x204/0x480 > [<00000000003b53ea>] __vfs_read+0x32/0x178 > [<00000000003b55b2>] vfs_read+0x82/0x138 > [<00000000003b5be2>] ksys_read+0x5a/0xb0 > [<0000000000b86ba0>] system_call+0xdc/0x2d8 > Last Breaking-Event-Address: > [<000000000038596c>] is_mem_section_removable+0xb4/0x190 > Kernel panic - not syncing: Fatal exception: panic_on_oops > >Fix the problem by initializing the last memory section of each zone >in memmap_init_zone() till the very end, even if it goes beyond the zone >end. > >Signed-off-by: Mikhail Zaslonko <zaslo...@linux.ibm.com> >Reviewed-by: Gerald Schaefer <gerald.schae...@de.ibm.com> >Cc: <sta...@vger.kernel.org> >--- > mm/page_alloc.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > >diff --git a/mm/page_alloc.c b/mm/page_alloc.c >index 2ec9cc407216..e2afdb2dc2c5 100644 >--- a/mm/page_alloc.c >+++ b/mm/page_alloc.c >@@ -5542,6 +5542,18 @@ void __meminit memmap_init_zone(unsigned long size, int >nid, unsigned long zone, > cond_resched(); > } > } >+#ifdef CONFIG_SPARSEMEM >+ /* >+ * If the zone does not span the rest of the section then >+ * we should at least initialize those pages. Otherwise we >+ * could blow up on a poisoned page in some paths which depend >+ * on full sections being initialized (e.g. memory hotplug). >+ */ >+ while (end_pfn % PAGES_PER_SECTION) { >+ __init_single_page(pfn_to_page(end_pfn), end_pfn, zone, nid); >+ end_pfn++; >+ } >+#endif > }
What will happen if the end_pfn is PAGES_PER_SECTION aligned, but there is invalid pfn? For example, the page is skipped in the for loop of memmap_init_zone()? > > #ifdef CONFIG_ZONE_DEVICE >-- >2.16.4 -- Wei Yang Help you, Help me