From: David Hildenbrand <david@xxxxxxxxxx> Subject: mm/memory_hotplug: make unregister_memory_block_under_nodes() never fail We really don't want anything during memory hotunplug to fail. We always pass a valid memory block device, that check can go. Avoid allocating memory and eventually failing. As we are always called under lock, we can use a static piece of memory. This avoids having to put the structure onto the stack, having to guess about the stack size of callers. Patch inspired by a patch from Oscar Salvador. In the future, there might be no need to iterate over nodes at all. mem->nid should tell us exactly what to remove. Memory block devices with mixed nodes (added during boot) should properly fenced off and never removed. Link: http://lkml.kernel.org/r/20190527111152.16324-11-david@xxxxxxxxxx Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx> 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: Alex Deucher <alexander.deucher@xxxxxxx> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> Cc: Mark Brown <broonie@xxxxxxxxxx> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> Cc: Andrew Banman <andrew.banman@xxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> Cc: Arun KS <arunks@xxxxxxxxxxxxxx> Cc: Baoquan He <bhe@xxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Chintan Pandya <cpandya@xxxxxxxxxxxxxx> Cc: Christophe Leroy <christophe.leroy@xxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Jun Yao <yaojun8558363@xxxxxxxxx> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> Cc: Mathieu Malaterre <malat@xxxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: "mike.travis@xxxxxxx" <mike.travis@xxxxxxx> Cc: Nicholas Piggin <npiggin@xxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Qian Cai <cai@xxxxxx> Cc: Rich Felker <dalias@xxxxxxxx> Cc: Rob Herring <robh@xxxxxxxxxx> Cc: Robin Murphy <robin.murphy@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> Cc: Will Deacon <will.deacon@xxxxxxx> Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx> Cc: Yu Zhao <yuzhao@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/base/node.c | 18 +++++------------- include/linux/node.h | 5 ++--- 2 files changed, 7 insertions(+), 16 deletions(-) --- a/drivers/base/node.c~mm-memory_hotplug-make-unregister_memory_block_under_nodes-never-fail +++ a/drivers/base/node.c @@ -804,20 +804,14 @@ int register_mem_sect_under_node(struct /* * Unregister memory block device under all nodes that it spans. + * Has to be called with mem_sysfs_mutex held (due to unlinked_nodes). */ -int unregister_memory_block_under_nodes(struct memory_block *mem_blk) +void unregister_memory_block_under_nodes(struct memory_block *mem_blk) { - NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL); unsigned long pfn, sect_start_pfn, sect_end_pfn; + static nodemask_t unlinked_nodes; - if (!mem_blk) { - NODEMASK_FREE(unlinked_nodes); - return -EFAULT; - } - if (!unlinked_nodes) - return -ENOMEM; - nodes_clear(*unlinked_nodes); - + nodes_clear(unlinked_nodes); sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr); sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr); for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) { @@ -828,15 +822,13 @@ int unregister_memory_block_under_nodes( continue; if (!node_online(nid)) continue; - if (node_test_and_set(nid, *unlinked_nodes)) + if (node_test_and_set(nid, unlinked_nodes)) continue; sysfs_remove_link(&node_devices[nid]->dev.kobj, kobject_name(&mem_blk->dev.kobj)); sysfs_remove_link(&mem_blk->dev.kobj, kobject_name(&node_devices[nid]->dev.kobj)); } - NODEMASK_FREE(unlinked_nodes); - return 0; } int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn) --- a/include/linux/node.h~mm-memory_hotplug-make-unregister_memory_block_under_nodes-never-fail +++ a/include/linux/node.h @@ -139,7 +139,7 @@ extern int register_cpu_under_node(unsig extern int unregister_cpu_under_node(unsigned int cpu, unsigned int nid); extern int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg); -extern int unregister_memory_block_under_nodes(struct memory_block *mem_blk); +extern void unregister_memory_block_under_nodes(struct memory_block *mem_blk); extern int register_memory_node_under_compute_node(unsigned int mem_nid, unsigned int cpu_nid, @@ -175,9 +175,8 @@ static inline int register_mem_sect_unde { return 0; } -static inline int unregister_memory_block_under_nodes(struct memory_block *mem_blk) +static inline void unregister_memory_block_under_nodes(struct memory_block *mem_blk) { - return 0; } static inline void register_hugetlbfs_with_node(node_registration_func_t reg, _
