From: Laurent Dufour <ldufour@xxxxxxxxxxxxx> Subject: mm: replace memmap_context by meminit_context Patch series "mm: fix memory to node bad links in sysfs", v3. Sometimes, firmware may expose interleaved memory layout like this: Early memory node ranges node 1: [mem 0x0000000000000000-0x000000011fffffff] node 2: [mem 0x0000000120000000-0x000000014fffffff] node 1: [mem 0x0000000150000000-0x00000001ffffffff] node 0: [mem 0x0000000200000000-0x000000048fffffff] node 2: [mem 0x0000000490000000-0x00000007ffffffff] In that case, we can see memory blocks assigned to multiple nodes in sysfs: $ ls -l /sys/devices/system/memory/memory21 total 0 lrwxrwxrwx 1 root root 0 Aug 24 05:27 node1 -> ../../node/node1 lrwxrwxrwx 1 root root 0 Aug 24 05:27 node2 -> ../../node/node2 -rw-r--r-- 1 root root 65536 Aug 24 05:27 online -r--r--r-- 1 root root 65536 Aug 24 05:27 phys_device -r--r--r-- 1 root root 65536 Aug 24 05:27 phys_index drwxr-xr-x 2 root root 0 Aug 24 05:27 power -r--r--r-- 1 root root 65536 Aug 24 05:27 removable -rw-r--r-- 1 root root 65536 Aug 24 05:27 state lrwxrwxrwx 1 root root 0 Aug 24 05:25 subsystem -> ../../../../bus/memory -rw-r--r-- 1 root root 65536 Aug 24 05:25 uevent -r--r--r-- 1 root root 65536 Aug 24 05:27 valid_zones The same applies in the node's directory with a memory21 link in both the node1 and node2's directory. This is wrong but doesn't prevent the system to run. However when later, one of these memory blocks is hot-unplugged and then hot-plugged, the system is detecting an inconsistency in the sysfs layout and a BUG_ON() is raised: ------------[ cut here ]------------ kernel BUG at /Users/laurent/src/linux-ppc/mm/memory_hotplug.c:1084! Oops: Exception in kernel mode, sig: 5 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Modules linked in: rpadlpar_io rpaphp pseries_rng rng_core vmx_crypto gf128mul binfmt_misc ip_tables x_tables xfs libcrc32c crc32c_vpmsum autofs4 CPU: 8 PID: 10256 Comm: drmgr Not tainted 5.9.0-rc1+ #25 NIP: c000000000403f34 LR: c000000000403f2c CTR: 0000000000000000 REGS: c0000004876e3660 TRAP: 0700 Not tainted (5.9.0-rc1+) MSR: 800000000282b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 24000448 XER: 20040000 CFAR: c000000000846d20 IRQMASK: 0 GPR00: c000000000403f2c c0000004876e38f0 c0000000012f6f00 ffffffffffffffef GPR04: 0000000000000227 c0000004805ae680 0000000000000000 00000004886f0000 GPR08: 0000000000000226 0000000000000003 0000000000000002 fffffffffffffffd GPR12: 0000000088000484 c00000001ec96280 0000000000000000 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000004 0000000000000003 GPR20: c00000047814ffe0 c0000007ffff7c08 0000000000000010 c0000000013332c8 GPR24: 0000000000000000 c0000000011f6cc0 0000000000000000 0000000000000000 GPR28: ffffffffffffffef 0000000000000001 0000000150000000 0000000010000000 NIP [c000000000403f34] add_memory_resource+0x244/0x340 LR [c000000000403f2c] add_memory_resource+0x23c/0x340 Call Trace: [c0000004876e38f0] [c000000000403f2c] add_memory_resource+0x23c/0x340 (unreliable) [c0000004876e39c0] [c00000000040408c] __add_memory+0x5c/0xf0 [c0000004876e39f0] [c0000000000e2b94] dlpar_add_lmb+0x1b4/0x500 [c0000004876e3ad0] [c0000000000e3888] dlpar_memory+0x1f8/0xb80 [c0000004876e3b60] [c0000000000dc0d0] handle_dlpar_errorlog+0xc0/0x190 [c0000004876e3bd0] [c0000000000dc398] dlpar_store+0x198/0x4a0 [c0000004876e3c90] [c00000000072e630] kobj_attr_store+0x30/0x50 [c0000004876e3cb0] [c00000000051f954] sysfs_kf_write+0x64/0x90 [c0000004876e3cd0] [c00000000051ee40] kernfs_fop_write+0x1b0/0x290 [c0000004876e3d20] [c000000000438dd8] vfs_write+0xe8/0x290 [c0000004876e3d70] [c0000000004391ac] ksys_write+0xdc/0x130 [c0000004876e3dc0] [c000000000034e40] system_call_exception+0x160/0x270 [c0000004876e3e20] [c00000000000d740] system_call_common+0xf0/0x27c Instruction dump: 48442e35 60000000 0b030000 3cbe0001 7fa3eb78 7bc48402 38a5fffe 7ca5fa14 78a58402 48442db1 60000000 7c7c1b78 <0b030000> 7f23cb78 4bda371d 60000000 ---[ end trace 562fd6c109cd0fb2 ]--- This has been seen on PowerPC LPAR. The root cause of this issue is that when node's memory is registered, the range used can overlap another node's range, thus the memory block is registered to multiple nodes in sysfs. There are 2 issues here: a. The sysfs memory and node's layouts are broken due to these multiple links b. The link errors in link_mem_sections() should not lead to a system panic. To address a. register_mem_sect_under_node should not rely on the system state to detect whether the link operation is triggered by a hot plug operation or not. This is addressed by the patches 1 and 2 of this series. The patch 3 is addressing the point b. This patch (of 2): The memmap_context enum is used to detect whether a memory operation is due to a hot-add operation or happening at boot time. Make it general to the hotplug operation and rename it as meminit_context. There is no functional change introduced by this patch Link: https://lkml.kernel.org/r/20200915094143.79181-1-ldufour@xxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20200915132624.9723-1-ldufour@xxxxxxxxxxxxx Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxx> Suggested-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: "Rafael J . Wysocki" <rafael@xxxxxxxxxx> Cc: Nathan Lynch <nathanl@xxxxxxxxxxxxx> Cc: Scott Cheloha <cheloha@xxxxxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/ia64/mm/init.c | 6 +++--- include/linux/mm.h | 2 +- include/linux/mmzone.h | 11 ++++++++--- mm/memory_hotplug.c | 2 +- mm/page_alloc.c | 10 +++++----- 5 files changed, 18 insertions(+), 13 deletions(-) --- a/arch/ia64/mm/init.c~mm-replace-memmap_context-by-meminit_context +++ a/arch/ia64/mm/init.c @@ -538,7 +538,7 @@ virtual_memmap_init(u64 start, u64 end, if (map_start < map_end) memmap_init_zone((unsigned long)(map_end - map_start), args->nid, args->zone, page_to_pfn(map_start), - MEMMAP_EARLY, NULL); + MEMINIT_EARLY, NULL); return 0; } @@ -547,8 +547,8 @@ memmap_init (unsigned long size, int nid unsigned long start_pfn) { if (!vmem_map) { - memmap_init_zone(size, nid, zone, start_pfn, MEMMAP_EARLY, - NULL); + memmap_init_zone(size, nid, zone, start_pfn, + MEMINIT_EARLY, NULL); } else { struct page *start; struct memmap_init_callback_data args; --- a/include/linux/mm.h~mm-replace-memmap_context-by-meminit_context +++ a/include/linux/mm.h @@ -2416,7 +2416,7 @@ extern int __meminit __early_pfn_to_nid( extern void set_dma_reserve(unsigned long new_dma_reserve); extern void memmap_init_zone(unsigned long, int, unsigned long, unsigned long, - enum memmap_context, struct vmem_altmap *); + enum meminit_context, struct vmem_altmap *); extern void setup_per_zone_wmarks(void); extern int __meminit init_per_zone_wmark_min(void); extern void mem_init(void); --- a/include/linux/mmzone.h~mm-replace-memmap_context-by-meminit_context +++ a/include/linux/mmzone.h @@ -824,10 +824,15 @@ bool zone_watermark_ok(struct zone *z, u unsigned int alloc_flags); bool zone_watermark_ok_safe(struct zone *z, unsigned int order, unsigned long mark, int highest_zoneidx); -enum memmap_context { - MEMMAP_EARLY, - MEMMAP_HOTPLUG, +/* + * Memory initialization context, use to differentiate memory added by + * the platform statically or via memory hotplug interface. + */ +enum meminit_context { + MEMINIT_EARLY, + MEMINIT_HOTPLUG, }; + extern void init_currently_empty_zone(struct zone *zone, unsigned long start_pfn, unsigned long size); --- a/mm/memory_hotplug.c~mm-replace-memmap_context-by-meminit_context +++ a/mm/memory_hotplug.c @@ -729,7 +729,7 @@ void __ref move_pfn_range_to_zone(struct * are reserved so nobody should be touching them so we should be safe */ memmap_init_zone(nr_pages, nid, zone_idx(zone), start_pfn, - MEMMAP_HOTPLUG, altmap); + MEMINIT_HOTPLUG, altmap); set_zone_contiguous(zone); } --- a/mm/page_alloc.c~mm-replace-memmap_context-by-meminit_context +++ a/mm/page_alloc.c @@ -5975,7 +5975,7 @@ overlap_memmap_init(unsigned long zone, * done. Non-atomic initialization, single-pass. */ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, - unsigned long start_pfn, enum memmap_context context, + unsigned long start_pfn, enum meminit_context context, struct vmem_altmap *altmap) { unsigned long pfn, end_pfn = start_pfn + size; @@ -6007,7 +6007,7 @@ void __meminit memmap_init_zone(unsigned * There can be holes in boot-time mem_map[]s handed to this * function. They do not exist on hotplugged memory. */ - if (context == MEMMAP_EARLY) { + if (context == MEMINIT_EARLY) { if (overlap_memmap_init(zone, &pfn)) continue; if (defer_init(nid, pfn, end_pfn)) @@ -6016,7 +6016,7 @@ void __meminit memmap_init_zone(unsigned page = pfn_to_page(pfn); __init_single_page(page, pfn, zone, nid); - if (context == MEMMAP_HOTPLUG) + if (context == MEMINIT_HOTPLUG) __SetPageReserved(page); /* @@ -6099,7 +6099,7 @@ void __ref memmap_init_zone_device(struc * check here not to call set_pageblock_migratetype() against * pfn out of zone. * - * Please note that MEMMAP_HOTPLUG path doesn't clear memmap + * Please note that MEMINIT_HOTPLUG path doesn't clear memmap * because this is done early in section_activate() */ if (!(pfn & (pageblock_nr_pages - 1))) { @@ -6137,7 +6137,7 @@ void __meminit __weak memmap_init(unsign if (end_pfn > start_pfn) { size = end_pfn - start_pfn; memmap_init_zone(size, nid, zone, start_pfn, - MEMMAP_EARLY, NULL); + MEMINIT_EARLY, NULL); } } } _
