| Message ID | 155977187407.2443951.16503493275720588454.stgit@dwillia2-desk3.amr.corp.intel.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | mm: Sub-section memory hotplug support | expand |
On Wed, Jun 05, 2019 at 02:57:54PM -0700, Dan Williams wrote: > Towards enabling memory hotplug to track partial population of a > section, introduce 'struct mem_section_usage'. > > A pointer to a 'struct mem_section_usage' instance replaces the existing > pointer to a 'pageblock_flags' bitmap. Effectively it adds one more > 'unsigned long' beyond the 'pageblock_flags' (usemap) allocation to > house a new 'subsection_map' bitmap. The new bitmap enables the memory > hot{plug,remove} implementation to act on incremental sub-divisions of a > section. > > The default SUBSECTION_SHIFT is chosen to keep the 'subsection_map' no > larger than a single 'unsigned long' on the major architectures. > Alternatively an architecture can define ARCH_SUBSECTION_SHIFT to > override the default PMD_SHIFT. Note that PowerPC needs to use > ARCH_SUBSECTION_SHIFT to workaround PMD_SHIFT being a non-constant > expression on PowerPC. > > The primary motivation for this functionality is to support platforms > that mix "System RAM" and "Persistent Memory" within a single section, > or multiple PMEM ranges with different mapping lifetimes within a single > section. The section restriction for hotplug has caused an ongoing saga > of hacks and bugs for devm_memremap_pages() users. > > Beyond the fixups to teach existing paths how to retrieve the 'usemap' > from a section, and updates to usemap allocation path, there are no > expected behavior changes. > > Cc: Michal Hocko <mhocko@suse.com> > Cc: Vlastimil Babka <vbabka@suse.cz> > Cc: Logan Gunthorpe <logang@deltatee.com> > Cc: Oscar Salvador <osalvador@suse.de> > Cc: Pavel Tatashin <pasha.tatashin@soleen.com> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Paul Mackerras <paulus@samba.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: Oscar Salvador <osalvador@suse.de>
On Wed, Jun 05, 2019 at 02:57:54PM -0700, Dan Williams wrote: >Towards enabling memory hotplug to track partial population of a >section, introduce 'struct mem_section_usage'. > >A pointer to a 'struct mem_section_usage' instance replaces the existing >pointer to a 'pageblock_flags' bitmap. Effectively it adds one more >'unsigned long' beyond the 'pageblock_flags' (usemap) allocation to >house a new 'subsection_map' bitmap. The new bitmap enables the memory >hot{plug,remove} implementation to act on incremental sub-divisions of a >section. > >The default SUBSECTION_SHIFT is chosen to keep the 'subsection_map' no >larger than a single 'unsigned long' on the major architectures. >Alternatively an architecture can define ARCH_SUBSECTION_SHIFT to >override the default PMD_SHIFT. Note that PowerPC needs to use >ARCH_SUBSECTION_SHIFT to workaround PMD_SHIFT being a non-constant >expression on PowerPC. > >The primary motivation for this functionality is to support platforms >that mix "System RAM" and "Persistent Memory" within a single section, >or multiple PMEM ranges with different mapping lifetimes within a single >section. The section restriction for hotplug has caused an ongoing saga >of hacks and bugs for devm_memremap_pages() users. > >Beyond the fixups to teach existing paths how to retrieve the 'usemap' >from a section, and updates to usemap allocation path, there are no >expected behavior changes. > >Cc: Michal Hocko <mhocko@suse.com> >Cc: Vlastimil Babka <vbabka@suse.cz> >Cc: Logan Gunthorpe <logang@deltatee.com> >Cc: Oscar Salvador <osalvador@suse.de> >Cc: Pavel Tatashin <pasha.tatashin@soleen.com> >Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> >Cc: Paul Mackerras <paulus@samba.org> >Cc: Michael Ellerman <mpe@ellerman.id.au> >Signed-off-by: Dan Williams <dan.j.williams@intel.com> >--- > arch/powerpc/include/asm/sparsemem.h | 3 + > include/linux/mmzone.h | 48 +++++++++++++++++++- > mm/memory_hotplug.c | 18 ++++---- > mm/page_alloc.c | 2 - > mm/sparse.c | 81 +++++++++++++++++----------------- > 5 files changed, 99 insertions(+), 53 deletions(-) > >diff --git a/arch/powerpc/include/asm/sparsemem.h b/arch/powerpc/include/asm/sparsemem.h >index 3192d454a733..1aa3c9303bf8 100644 >--- a/arch/powerpc/include/asm/sparsemem.h >+++ b/arch/powerpc/include/asm/sparsemem.h >@@ -10,6 +10,9 @@ > */ > #define SECTION_SIZE_BITS 24 > >+/* Reflect the largest possible PMD-size as the subsection-size constant */ >+#define ARCH_SUBSECTION_SHIFT 24 >+ > #endif /* CONFIG_SPARSEMEM */ > > #ifdef CONFIG_MEMORY_HOTPLUG >diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >index 427b79c39b3c..ac163f2f274f 100644 >--- a/include/linux/mmzone.h >+++ b/include/linux/mmzone.h >@@ -1161,6 +1161,44 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec) > #define SECTION_ALIGN_UP(pfn) (((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK) > #define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK) > >+/* >+ * SUBSECTION_SHIFT must be constant since it is used to declare >+ * subsection_map and related bitmaps without triggering the generation >+ * of variable-length arrays. The most natural size for a subsection is >+ * a PMD-page. For architectures that do not have a constant PMD-size >+ * ARCH_SUBSECTION_SHIFT can be set to a constant max size, or otherwise >+ * fallback to 2MB. >+ */ >+#if defined(ARCH_SUBSECTION_SHIFT) >+#define SUBSECTION_SHIFT (ARCH_SUBSECTION_SHIFT) >+#elif defined(PMD_SHIFT) >+#define SUBSECTION_SHIFT (PMD_SHIFT) >+#else >+/* >+ * Memory hotplug enabled platforms avoid this default because they >+ * either define ARCH_SUBSECTION_SHIFT, or PMD_SHIFT is a constant, but >+ * this is kept as a backstop to allow compilation on >+ * !ARCH_ENABLE_MEMORY_HOTPLUG archs. >+ */ >+#define SUBSECTION_SHIFT 21 >+#endif >+ >+#define PFN_SUBSECTION_SHIFT (SUBSECTION_SHIFT - PAGE_SHIFT) >+#define PAGES_PER_SUBSECTION (1UL << PFN_SUBSECTION_SHIFT) >+#define PAGE_SUBSECTION_MASK ((~(PAGES_PER_SUBSECTION-1))) One pair of brackets could be removed, IMHO. >+ >+#if SUBSECTION_SHIFT > SECTION_SIZE_BITS >+#error Subsection size exceeds section size >+#else >+#define SUBSECTIONS_PER_SECTION (1UL << (SECTION_SIZE_BITS - SUBSECTION_SHIFT)) >+#endif >+ >+struct mem_section_usage { >+ DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION); >+ /* See declaration of similar field in struct zone */ >+ unsigned long pageblock_flags[0]; >+}; >+ > struct page; > struct page_ext; > struct mem_section { >@@ -1178,8 +1216,7 @@ struct mem_section { > */ > unsigned long section_mem_map; > >- /* See declaration of similar field in struct zone */ >- unsigned long *pageblock_flags; >+ struct mem_section_usage *usage; > #ifdef CONFIG_PAGE_EXTENSION > /* > * If SPARSEMEM, pgdat doesn't have page_ext pointer. We use >@@ -1210,6 +1247,11 @@ extern struct mem_section **mem_section; > extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]; > #endif > >+static inline unsigned long *section_to_usemap(struct mem_section *ms) >+{ >+ return ms->usage->pageblock_flags; Do we need to consider the case when ms->usage is NULL? >+} >+ > static inline struct mem_section *__nr_to_section(unsigned long nr) > { > #ifdef CONFIG_SPARSEMEM_EXTREME >@@ -1221,7 +1263,7 @@ static inline struct mem_section *__nr_to_section(unsigned long nr) > return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK]; > } > extern int __section_nr(struct mem_section* ms); >-extern unsigned long usemap_size(void); >+extern size_t mem_section_usage_size(void); > > /* > * We use the lower bits of the mem_map pointer to store >diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >index a88c5f334e5a..7b963c2d3a0d 100644 >--- a/mm/memory_hotplug.c >+++ b/mm/memory_hotplug.c >@@ -166,9 +166,10 @@ void put_page_bootmem(struct page *page) > #ifndef CONFIG_SPARSEMEM_VMEMMAP > static void register_page_bootmem_info_section(unsigned long start_pfn) > { >- unsigned long *usemap, mapsize, section_nr, i; >+ unsigned long mapsize, section_nr, i; > struct mem_section *ms; > struct page *page, *memmap; >+ struct mem_section_usage *usage; > > section_nr = pfn_to_section_nr(start_pfn); > ms = __nr_to_section(section_nr); >@@ -188,10 +189,10 @@ static void register_page_bootmem_info_section(unsigned long start_pfn) > for (i = 0; i < mapsize; i++, page++) > get_page_bootmem(section_nr, page, SECTION_INFO); > >- usemap = ms->pageblock_flags; >- page = virt_to_page(usemap); >+ usage = ms->usage; >+ page = virt_to_page(usage); > >- mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT; >+ mapsize = PAGE_ALIGN(mem_section_usage_size()) >> PAGE_SHIFT; > > for (i = 0; i < mapsize; i++, page++) > get_page_bootmem(section_nr, page, MIX_SECTION_INFO); >@@ -200,9 +201,10 @@ static void register_page_bootmem_info_section(unsigned long start_pfn) > #else /* CONFIG_SPARSEMEM_VMEMMAP */ > static void register_page_bootmem_info_section(unsigned long start_pfn) > { >- unsigned long *usemap, mapsize, section_nr, i; >+ unsigned long mapsize, section_nr, i; > struct mem_section *ms; > struct page *page, *memmap; >+ struct mem_section_usage *usage; > > section_nr = pfn_to_section_nr(start_pfn); > ms = __nr_to_section(section_nr); >@@ -211,10 +213,10 @@ static void register_page_bootmem_info_section(unsigned long start_pfn) > > register_page_bootmem_memmap(section_nr, memmap, PAGES_PER_SECTION); > >- usemap = ms->pageblock_flags; >- page = virt_to_page(usemap); >+ usage = ms->usage; >+ page = virt_to_page(usage); > >- mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT; >+ mapsize = PAGE_ALIGN(mem_section_usage_size()) >> PAGE_SHIFT; > > for (i = 0; i < mapsize; i++, page++) > get_page_bootmem(section_nr, page, MIX_SECTION_INFO); >diff --git a/mm/page_alloc.c b/mm/page_alloc.c >index c061f66c2d0c..c6d8224d792e 100644 >--- a/mm/page_alloc.c >+++ b/mm/page_alloc.c >@@ -404,7 +404,7 @@ static inline unsigned long *get_pageblock_bitmap(struct page *page, > unsigned long pfn) > { > #ifdef CONFIG_SPARSEMEM >- return __pfn_to_section(pfn)->pageblock_flags; >+ return section_to_usemap(__pfn_to_section(pfn)); > #else > return page_zone(page)->pageblock_flags; > #endif /* CONFIG_SPARSEMEM */ >diff --git a/mm/sparse.c b/mm/sparse.c >index 1552c855d62a..71da15cc7432 100644 >--- a/mm/sparse.c >+++ b/mm/sparse.c >@@ -288,33 +288,31 @@ struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pn > > static void __meminit sparse_init_one_section(struct mem_section *ms, > unsigned long pnum, struct page *mem_map, >- unsigned long *pageblock_bitmap) >+ struct mem_section_usage *usage) > { > ms->section_mem_map &= ~SECTION_MAP_MASK; > ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum) | > SECTION_HAS_MEM_MAP; >- ms->pageblock_flags = pageblock_bitmap; >+ ms->usage = usage; > } > >-unsigned long usemap_size(void) >+static unsigned long usemap_size(void) > { > return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long); > } > >-#ifdef CONFIG_MEMORY_HOTPLUG >-static unsigned long *__kmalloc_section_usemap(void) >+size_t mem_section_usage_size(void) > { >- return kmalloc(usemap_size(), GFP_KERNEL); >+ return sizeof(struct mem_section_usage) + usemap_size(); > } >-#endif /* CONFIG_MEMORY_HOTPLUG */ > > #ifdef CONFIG_MEMORY_HOTREMOVE >-static unsigned long * __init >+static struct mem_section_usage * __init > sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, > unsigned long size) > { >+ struct mem_section_usage *usage; > unsigned long goal, limit; >- unsigned long *p; > int nid; > /* > * A page may contain usemaps for other sections preventing the >@@ -330,15 +328,16 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, > limit = goal + (1UL << PA_SECTION_SHIFT); > nid = early_pfn_to_nid(goal >> PAGE_SHIFT); > again: >- p = memblock_alloc_try_nid(size, SMP_CACHE_BYTES, goal, limit, nid); >- if (!p && limit) { >+ usage = memblock_alloc_try_nid(size, SMP_CACHE_BYTES, goal, limit, nid); >+ if (!usage && limit) { > limit = 0; > goto again; > } >- return p; >+ return usage; > } > >-static void __init check_usemap_section_nr(int nid, unsigned long *usemap) >+static void __init check_usemap_section_nr(int nid, >+ struct mem_section_usage *usage) > { > unsigned long usemap_snr, pgdat_snr; > static unsigned long old_usemap_snr; >@@ -352,7 +351,7 @@ static void __init check_usemap_section_nr(int nid, unsigned long *usemap) > old_pgdat_snr = NR_MEM_SECTIONS; > } > >- usemap_snr = pfn_to_section_nr(__pa(usemap) >> PAGE_SHIFT); >+ usemap_snr = pfn_to_section_nr(__pa(usage) >> PAGE_SHIFT); > pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT); > if (usemap_snr == pgdat_snr) > return; >@@ -380,14 +379,15 @@ static void __init check_usemap_section_nr(int nid, unsigned long *usemap) > usemap_snr, pgdat_snr, nid); > } > #else >-static unsigned long * __init >+static struct mem_section_usage * __init > sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, > unsigned long size) > { > return memblock_alloc_node(size, SMP_CACHE_BYTES, pgdat->node_id); > } > >-static void __init check_usemap_section_nr(int nid, unsigned long *usemap) >+static void __init check_usemap_section_nr(int nid, >+ struct mem_section_usage *usage) > { > } > #endif /* CONFIG_MEMORY_HOTREMOVE */ >@@ -474,14 +474,13 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin, > unsigned long pnum_end, > unsigned long map_count) > { >- unsigned long pnum, usemap_longs, *usemap; >+ struct mem_section_usage *usage; >+ unsigned long pnum; > struct page *map; > >- usemap_longs = BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS); >- usemap = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nid), >- usemap_size() * >- map_count); >- if (!usemap) { >+ usage = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nid), >+ mem_section_usage_size() * map_count); >+ if (!usage) { > pr_err("%s: node[%d] usemap allocation failed", __func__, nid); > goto failed; > } >@@ -497,9 +496,9 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin, > pnum_begin = pnum; > goto failed; > } >- check_usemap_section_nr(nid, usemap); >- sparse_init_one_section(__nr_to_section(pnum), pnum, map, usemap); >- usemap += usemap_longs; >+ check_usemap_section_nr(nid, usage); >+ sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage); >+ usage = (void *) usage + mem_section_usage_size(); > } > sparse_buffer_fini(); > return; >@@ -697,9 +696,9 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, > struct vmem_altmap *altmap) > { > unsigned long section_nr = pfn_to_section_nr(start_pfn); >+ struct mem_section_usage *usage; > struct mem_section *ms; > struct page *memmap; >- unsigned long *usemap; > int ret; > > /* >@@ -713,8 +712,8 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, > memmap = kmalloc_section_memmap(section_nr, nid, altmap); > if (!memmap) > return -ENOMEM; >- usemap = __kmalloc_section_usemap(); >- if (!usemap) { >+ usage = kzalloc(mem_section_usage_size(), GFP_KERNEL); >+ if (!usage) { > __kfree_section_memmap(memmap, altmap); > return -ENOMEM; > } >@@ -732,11 +731,11 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, > page_init_poison(memmap, sizeof(struct page) * PAGES_PER_SECTION); > > section_mark_present(ms); >- sparse_init_one_section(ms, section_nr, memmap, usemap); >+ sparse_init_one_section(ms, section_nr, memmap, usage); > > out: > if (ret < 0) { >- kfree(usemap); >+ kfree(usage); > __kfree_section_memmap(memmap, altmap); > } > return ret; >@@ -772,20 +771,20 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages) > } > #endif > >-static void free_section_usemap(struct page *memmap, unsigned long *usemap, >- struct vmem_altmap *altmap) >+static void free_section_usage(struct page *memmap, >+ struct mem_section_usage *usage, struct vmem_altmap *altmap) > { >- struct page *usemap_page; >+ struct page *usage_page; > >- if (!usemap) >+ if (!usage) > return; > >- usemap_page = virt_to_page(usemap); >+ usage_page = virt_to_page(usage); > /* > * Check to see if allocation came from hot-plug-add > */ >- if (PageSlab(usemap_page) || PageCompound(usemap_page)) { >- kfree(usemap); >+ if (PageSlab(usage_page) || PageCompound(usage_page)) { >+ kfree(usage); > if (memmap) > __kfree_section_memmap(memmap, altmap); > return; >@@ -804,18 +803,18 @@ void sparse_remove_one_section(struct mem_section *ms, unsigned long map_offset, > struct vmem_altmap *altmap) > { > struct page *memmap = NULL; >- unsigned long *usemap = NULL; >+ struct mem_section_usage *usage = NULL; > > if (ms->section_mem_map) { >- usemap = ms->pageblock_flags; >+ usage = ms->usage; > memmap = sparse_decode_mem_map(ms->section_mem_map, > __section_nr(ms)); > ms->section_mem_map = 0; >- ms->pageblock_flags = NULL; >+ ms->usage = NULL; > } > > clear_hwpoisoned_pages(memmap + map_offset, > PAGES_PER_SECTION - map_offset); >- free_section_usemap(memmap, usemap, altmap); >+ free_section_usage(memmap, usage, altmap); > } > #endif /* CONFIG_MEMORY_HOTPLUG */
On Sun, Jun 16, 2019 at 6:11 AM Wei Yang <richard.weiyang@gmail.com> wrote: > > On Wed, Jun 05, 2019 at 02:57:54PM -0700, Dan Williams wrote: > >Towards enabling memory hotplug to track partial population of a > >section, introduce 'struct mem_section_usage'. > > > >A pointer to a 'struct mem_section_usage' instance replaces the existing > >pointer to a 'pageblock_flags' bitmap. Effectively it adds one more > >'unsigned long' beyond the 'pageblock_flags' (usemap) allocation to > >house a new 'subsection_map' bitmap. The new bitmap enables the memory > >hot{plug,remove} implementation to act on incremental sub-divisions of a > >section. > > > >The default SUBSECTION_SHIFT is chosen to keep the 'subsection_map' no > >larger than a single 'unsigned long' on the major architectures. > >Alternatively an architecture can define ARCH_SUBSECTION_SHIFT to > >override the default PMD_SHIFT. Note that PowerPC needs to use > >ARCH_SUBSECTION_SHIFT to workaround PMD_SHIFT being a non-constant > >expression on PowerPC. > > > >The primary motivation for this functionality is to support platforms > >that mix "System RAM" and "Persistent Memory" within a single section, > >or multiple PMEM ranges with different mapping lifetimes within a single > >section. The section restriction for hotplug has caused an ongoing saga > >of hacks and bugs for devm_memremap_pages() users. > > > >Beyond the fixups to teach existing paths how to retrieve the 'usemap' > >from a section, and updates to usemap allocation path, there are no > >expected behavior changes. > > > >Cc: Michal Hocko <mhocko@suse.com> > >Cc: Vlastimil Babka <vbabka@suse.cz> > >Cc: Logan Gunthorpe <logang@deltatee.com> > >Cc: Oscar Salvador <osalvador@suse.de> > >Cc: Pavel Tatashin <pasha.tatashin@soleen.com> > >Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > >Cc: Paul Mackerras <paulus@samba.org> > >Cc: Michael Ellerman <mpe@ellerman.id.au> > >Signed-off-by: Dan Williams <dan.j.williams@intel.com> > >--- > > arch/powerpc/include/asm/sparsemem.h | 3 + > > include/linux/mmzone.h | 48 +++++++++++++++++++- > > mm/memory_hotplug.c | 18 ++++---- > > mm/page_alloc.c | 2 - > > mm/sparse.c | 81 +++++++++++++++++----------------- > > 5 files changed, 99 insertions(+), 53 deletions(-) > > > >diff --git a/arch/powerpc/include/asm/sparsemem.h b/arch/powerpc/include/asm/sparsemem.h > >index 3192d454a733..1aa3c9303bf8 100644 > >--- a/arch/powerpc/include/asm/sparsemem.h > >+++ b/arch/powerpc/include/asm/sparsemem.h > >@@ -10,6 +10,9 @@ > > */ > > #define SECTION_SIZE_BITS 24 > > > >+/* Reflect the largest possible PMD-size as the subsection-size constant */ > >+#define ARCH_SUBSECTION_SHIFT 24 > >+ > > #endif /* CONFIG_SPARSEMEM */ > > > > #ifdef CONFIG_MEMORY_HOTPLUG > >diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > >index 427b79c39b3c..ac163f2f274f 100644 > >--- a/include/linux/mmzone.h > >+++ b/include/linux/mmzone.h > >@@ -1161,6 +1161,44 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec) > > #define SECTION_ALIGN_UP(pfn) (((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK) > > #define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK) > > > >+/* > >+ * SUBSECTION_SHIFT must be constant since it is used to declare > >+ * subsection_map and related bitmaps without triggering the generation > >+ * of variable-length arrays. The most natural size for a subsection is > >+ * a PMD-page. For architectures that do not have a constant PMD-size > >+ * ARCH_SUBSECTION_SHIFT can be set to a constant max size, or otherwise > >+ * fallback to 2MB. > >+ */ > >+#if defined(ARCH_SUBSECTION_SHIFT) > >+#define SUBSECTION_SHIFT (ARCH_SUBSECTION_SHIFT) > >+#elif defined(PMD_SHIFT) > >+#define SUBSECTION_SHIFT (PMD_SHIFT) > >+#else > >+/* > >+ * Memory hotplug enabled platforms avoid this default because they > >+ * either define ARCH_SUBSECTION_SHIFT, or PMD_SHIFT is a constant, but > >+ * this is kept as a backstop to allow compilation on > >+ * !ARCH_ENABLE_MEMORY_HOTPLUG archs. > >+ */ > >+#define SUBSECTION_SHIFT 21 > >+#endif > >+ > >+#define PFN_SUBSECTION_SHIFT (SUBSECTION_SHIFT - PAGE_SHIFT) > >+#define PAGES_PER_SUBSECTION (1UL << PFN_SUBSECTION_SHIFT) > >+#define PAGE_SUBSECTION_MASK ((~(PAGES_PER_SUBSECTION-1))) > > One pair of brackets could be removed, IMHO. Sure. > > >+ > >+#if SUBSECTION_SHIFT > SECTION_SIZE_BITS > >+#error Subsection size exceeds section size > >+#else > >+#define SUBSECTIONS_PER_SECTION (1UL << (SECTION_SIZE_BITS - SUBSECTION_SHIFT)) > >+#endif > >+ > >+struct mem_section_usage { > >+ DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION); > >+ /* See declaration of similar field in struct zone */ > >+ unsigned long pageblock_flags[0]; > >+}; > >+ > > struct page; > > struct page_ext; > > struct mem_section { > >@@ -1178,8 +1216,7 @@ struct mem_section { > > */ > > unsigned long section_mem_map; > > > >- /* See declaration of similar field in struct zone */ > >- unsigned long *pageblock_flags; > >+ struct mem_section_usage *usage; > > #ifdef CONFIG_PAGE_EXTENSION > > /* > > * If SPARSEMEM, pgdat doesn't have page_ext pointer. We use > >@@ -1210,6 +1247,11 @@ extern struct mem_section **mem_section; > > extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]; > > #endif > > > >+static inline unsigned long *section_to_usemap(struct mem_section *ms) > >+{ > >+ return ms->usage->pageblock_flags; > > Do we need to consider the case when ms->usage is NULL? No, this routine safely assumes it is always set.
On Tue, Jun 18, 2019 at 02:56:09PM -0700, Dan Williams wrote: >On Sun, Jun 16, 2019 at 6:11 AM Wei Yang <richard.weiyang@gmail.com> wrote: >> >> On Wed, Jun 05, 2019 at 02:57:54PM -0700, Dan Williams wrote: >> >Towards enabling memory hotplug to track partial population of a >> >section, introduce 'struct mem_section_usage'. >> > >> >A pointer to a 'struct mem_section_usage' instance replaces the existing >> >pointer to a 'pageblock_flags' bitmap. Effectively it adds one more >> >'unsigned long' beyond the 'pageblock_flags' (usemap) allocation to >> >house a new 'subsection_map' bitmap. The new bitmap enables the memory >> >hot{plug,remove} implementation to act on incremental sub-divisions of a >> >section. >> > >> >The default SUBSECTION_SHIFT is chosen to keep the 'subsection_map' no >> >larger than a single 'unsigned long' on the major architectures. >> >Alternatively an architecture can define ARCH_SUBSECTION_SHIFT to >> >override the default PMD_SHIFT. Note that PowerPC needs to use >> >ARCH_SUBSECTION_SHIFT to workaround PMD_SHIFT being a non-constant >> >expression on PowerPC. >> > >> >The primary motivation for this functionality is to support platforms >> >that mix "System RAM" and "Persistent Memory" within a single section, >> >or multiple PMEM ranges with different mapping lifetimes within a single >> >section. The section restriction for hotplug has caused an ongoing saga >> >of hacks and bugs for devm_memremap_pages() users. >> > >> >Beyond the fixups to teach existing paths how to retrieve the 'usemap' >> >from a section, and updates to usemap allocation path, there are no >> >expected behavior changes. >> > >> >Cc: Michal Hocko <mhocko@suse.com> >> >Cc: Vlastimil Babka <vbabka@suse.cz> >> >Cc: Logan Gunthorpe <logang@deltatee.com> >> >Cc: Oscar Salvador <osalvador@suse.de> >> >Cc: Pavel Tatashin <pasha.tatashin@soleen.com> >> >Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> >> >Cc: Paul Mackerras <paulus@samba.org> >> >Cc: Michael Ellerman <mpe@ellerman.id.au> >> >Signed-off-by: Dan Williams <dan.j.williams@intel.com> >> >--- >> > arch/powerpc/include/asm/sparsemem.h | 3 + >> > include/linux/mmzone.h | 48 +++++++++++++++++++- >> > mm/memory_hotplug.c | 18 ++++---- >> > mm/page_alloc.c | 2 - >> > mm/sparse.c | 81 +++++++++++++++++----------------- >> > 5 files changed, 99 insertions(+), 53 deletions(-) >> > >> >diff --git a/arch/powerpc/include/asm/sparsemem.h b/arch/powerpc/include/asm/sparsemem.h >> >index 3192d454a733..1aa3c9303bf8 100644 >> >--- a/arch/powerpc/include/asm/sparsemem.h >> >+++ b/arch/powerpc/include/asm/sparsemem.h >> >@@ -10,6 +10,9 @@ >> > */ >> > #define SECTION_SIZE_BITS 24 >> > >> >+/* Reflect the largest possible PMD-size as the subsection-size constant */ >> >+#define ARCH_SUBSECTION_SHIFT 24 >> >+ >> > #endif /* CONFIG_SPARSEMEM */ >> > >> > #ifdef CONFIG_MEMORY_HOTPLUG >> >diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >> >index 427b79c39b3c..ac163f2f274f 100644 >> >--- a/include/linux/mmzone.h >> >+++ b/include/linux/mmzone.h >> >@@ -1161,6 +1161,44 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec) >> > #define SECTION_ALIGN_UP(pfn) (((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK) >> > #define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK) >> > >> >+/* >> >+ * SUBSECTION_SHIFT must be constant since it is used to declare >> >+ * subsection_map and related bitmaps without triggering the generation >> >+ * of variable-length arrays. The most natural size for a subsection is >> >+ * a PMD-page. For architectures that do not have a constant PMD-size >> >+ * ARCH_SUBSECTION_SHIFT can be set to a constant max size, or otherwise >> >+ * fallback to 2MB. >> >+ */ >> >+#if defined(ARCH_SUBSECTION_SHIFT) >> >+#define SUBSECTION_SHIFT (ARCH_SUBSECTION_SHIFT) >> >+#elif defined(PMD_SHIFT) >> >+#define SUBSECTION_SHIFT (PMD_SHIFT) >> >+#else >> >+/* >> >+ * Memory hotplug enabled platforms avoid this default because they >> >+ * either define ARCH_SUBSECTION_SHIFT, or PMD_SHIFT is a constant, but >> >+ * this is kept as a backstop to allow compilation on >> >+ * !ARCH_ENABLE_MEMORY_HOTPLUG archs. >> >+ */ >> >+#define SUBSECTION_SHIFT 21 >> >+#endif >> >+ >> >+#define PFN_SUBSECTION_SHIFT (SUBSECTION_SHIFT - PAGE_SHIFT) >> >+#define PAGES_PER_SUBSECTION (1UL << PFN_SUBSECTION_SHIFT) >> >+#define PAGE_SUBSECTION_MASK ((~(PAGES_PER_SUBSECTION-1))) >> >> One pair of brackets could be removed, IMHO. > >Sure. > >> >> >+ >> >+#if SUBSECTION_SHIFT > SECTION_SIZE_BITS >> >+#error Subsection size exceeds section size >> >+#else >> >+#define SUBSECTIONS_PER_SECTION (1UL << (SECTION_SIZE_BITS - SUBSECTION_SHIFT)) >> >+#endif >> >+ >> >+struct mem_section_usage { >> >+ DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION); >> >+ /* See declaration of similar field in struct zone */ >> >+ unsigned long pageblock_flags[0]; >> >+}; >> >+ >> > struct page; >> > struct page_ext; >> > struct mem_section { >> >@@ -1178,8 +1216,7 @@ struct mem_section { >> > */ >> > unsigned long section_mem_map; >> > >> >- /* See declaration of similar field in struct zone */ >> >- unsigned long *pageblock_flags; >> >+ struct mem_section_usage *usage; >> > #ifdef CONFIG_PAGE_EXTENSION >> > /* >> > * If SPARSEMEM, pgdat doesn't have page_ext pointer. We use >> >@@ -1210,6 +1247,11 @@ extern struct mem_section **mem_section; >> > extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]; >> > #endif >> > >> >+static inline unsigned long *section_to_usemap(struct mem_section *ms) >> >+{ >> >+ return ms->usage->pageblock_flags; >> >> Do we need to consider the case when ms->usage is NULL? > >No, this routine safely assumes it is always set. Then everything looks good to me. Reviewed-by: Wei Yang <richardw.yang@linux.intel.com> >_______________________________________________ >Linux-nvdimm mailing list >Linux-nvdimm@lists.01.org >https://lists.01.org/mailman/listinfo/linux-nvdimm
diff --git a/arch/powerpc/include/asm/sparsemem.h b/arch/powerpc/include/asm/sparsemem.h index 3192d454a733..1aa3c9303bf8 100644 --- a/arch/powerpc/include/asm/sparsemem.h +++ b/arch/powerpc/include/asm/sparsemem.h @@ -10,6 +10,9 @@ */ #define SECTION_SIZE_BITS 24 +/* Reflect the largest possible PMD-size as the subsection-size constant */ +#define ARCH_SUBSECTION_SHIFT 24 + #endif /* CONFIG_SPARSEMEM */ #ifdef CONFIG_MEMORY_HOTPLUG diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 427b79c39b3c..ac163f2f274f 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1161,6 +1161,44 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec) #define SECTION_ALIGN_UP(pfn) (((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK) #define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK) +/* + * SUBSECTION_SHIFT must be constant since it is used to declare + * subsection_map and related bitmaps without triggering the generation + * of variable-length arrays. The most natural size for a subsection is + * a PMD-page. For architectures that do not have a constant PMD-size + * ARCH_SUBSECTION_SHIFT can be set to a constant max size, or otherwise + * fallback to 2MB. + */ +#if defined(ARCH_SUBSECTION_SHIFT) +#define SUBSECTION_SHIFT (ARCH_SUBSECTION_SHIFT) +#elif defined(PMD_SHIFT) +#define SUBSECTION_SHIFT (PMD_SHIFT) +#else +/* + * Memory hotplug enabled platforms avoid this default because they + * either define ARCH_SUBSECTION_SHIFT, or PMD_SHIFT is a constant, but + * this is kept as a backstop to allow compilation on + * !ARCH_ENABLE_MEMORY_HOTPLUG archs. + */ +#define SUBSECTION_SHIFT 21 +#endif + +#define PFN_SUBSECTION_SHIFT (SUBSECTION_SHIFT - PAGE_SHIFT) +#define PAGES_PER_SUBSECTION (1UL << PFN_SUBSECTION_SHIFT) +#define PAGE_SUBSECTION_MASK ((~(PAGES_PER_SUBSECTION-1))) + +#if SUBSECTION_SHIFT > SECTION_SIZE_BITS +#error Subsection size exceeds section size +#else +#define SUBSECTIONS_PER_SECTION (1UL << (SECTION_SIZE_BITS - SUBSECTION_SHIFT)) +#endif + +struct mem_section_usage { + DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION); + /* See declaration of similar field in struct zone */ + unsigned long pageblock_flags[0]; +}; + struct page; struct page_ext; struct mem_section { @@ -1178,8 +1216,7 @@ struct mem_section { */ unsigned long section_mem_map; - /* See declaration of similar field in struct zone */ - unsigned long *pageblock_flags; + struct mem_section_usage *usage; #ifdef CONFIG_PAGE_EXTENSION /* * If SPARSEMEM, pgdat doesn't have page_ext pointer. We use @@ -1210,6 +1247,11 @@ extern struct mem_section **mem_section; extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]; #endif +static inline unsigned long *section_to_usemap(struct mem_section *ms) +{ + return ms->usage->pageblock_flags; +} + static inline struct mem_section *__nr_to_section(unsigned long nr) { #ifdef CONFIG_SPARSEMEM_EXTREME @@ -1221,7 +1263,7 @@ static inline struct mem_section *__nr_to_section(unsigned long nr) return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK]; } extern int __section_nr(struct mem_section* ms); -extern unsigned long usemap_size(void); +extern size_t mem_section_usage_size(void); /* * We use the lower bits of the mem_map pointer to store diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index a88c5f334e5a..7b963c2d3a0d 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -166,9 +166,10 @@ void put_page_bootmem(struct page *page) #ifndef CONFIG_SPARSEMEM_VMEMMAP static void register_page_bootmem_info_section(unsigned long start_pfn) { - unsigned long *usemap, mapsize, section_nr, i; + unsigned long mapsize, section_nr, i; struct mem_section *ms; struct page *page, *memmap; + struct mem_section_usage *usage; section_nr = pfn_to_section_nr(start_pfn); ms = __nr_to_section(section_nr); @@ -188,10 +189,10 @@ static void register_page_bootmem_info_section(unsigned long start_pfn) for (i = 0; i < mapsize; i++, page++) get_page_bootmem(section_nr, page, SECTION_INFO); - usemap = ms->pageblock_flags; - page = virt_to_page(usemap); + usage = ms->usage; + page = virt_to_page(usage); - mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT; + mapsize = PAGE_ALIGN(mem_section_usage_size()) >> PAGE_SHIFT; for (i = 0; i < mapsize; i++, page++) get_page_bootmem(section_nr, page, MIX_SECTION_INFO); @@ -200,9 +201,10 @@ static void register_page_bootmem_info_section(unsigned long start_pfn) #else /* CONFIG_SPARSEMEM_VMEMMAP */ static void register_page_bootmem_info_section(unsigned long start_pfn) { - unsigned long *usemap, mapsize, section_nr, i; + unsigned long mapsize, section_nr, i; struct mem_section *ms; struct page *page, *memmap; + struct mem_section_usage *usage; section_nr = pfn_to_section_nr(start_pfn); ms = __nr_to_section(section_nr); @@ -211,10 +213,10 @@ static void register_page_bootmem_info_section(unsigned long start_pfn) register_page_bootmem_memmap(section_nr, memmap, PAGES_PER_SECTION); - usemap = ms->pageblock_flags; - page = virt_to_page(usemap); + usage = ms->usage; + page = virt_to_page(usage); - mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT; + mapsize = PAGE_ALIGN(mem_section_usage_size()) >> PAGE_SHIFT; for (i = 0; i < mapsize; i++, page++) get_page_bootmem(section_nr, page, MIX_SECTION_INFO); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index c061f66c2d0c..c6d8224d792e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -404,7 +404,7 @@ static inline unsigned long *get_pageblock_bitmap(struct page *page, unsigned long pfn) { #ifdef CONFIG_SPARSEMEM - return __pfn_to_section(pfn)->pageblock_flags; + return section_to_usemap(__pfn_to_section(pfn)); #else return page_zone(page)->pageblock_flags; #endif /* CONFIG_SPARSEMEM */ diff --git a/mm/sparse.c b/mm/sparse.c index 1552c855d62a..71da15cc7432 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -288,33 +288,31 @@ struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pn static void __meminit sparse_init_one_section(struct mem_section *ms, unsigned long pnum, struct page *mem_map, - unsigned long *pageblock_bitmap) + struct mem_section_usage *usage) { ms->section_mem_map &= ~SECTION_MAP_MASK; ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum) | SECTION_HAS_MEM_MAP; - ms->pageblock_flags = pageblock_bitmap; + ms->usage = usage; } -unsigned long usemap_size(void) +static unsigned long usemap_size(void) { return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long); } -#ifdef CONFIG_MEMORY_HOTPLUG -static unsigned long *__kmalloc_section_usemap(void) +size_t mem_section_usage_size(void) { - return kmalloc(usemap_size(), GFP_KERNEL); + return sizeof(struct mem_section_usage) + usemap_size(); } -#endif /* CONFIG_MEMORY_HOTPLUG */ #ifdef CONFIG_MEMORY_HOTREMOVE -static unsigned long * __init +static struct mem_section_usage * __init sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, unsigned long size) { + struct mem_section_usage *usage; unsigned long goal, limit; - unsigned long *p; int nid; /* * A page may contain usemaps for other sections preventing the @@ -330,15 +328,16 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, limit = goal + (1UL << PA_SECTION_SHIFT); nid = early_pfn_to_nid(goal >> PAGE_SHIFT); again: - p = memblock_alloc_try_nid(size, SMP_CACHE_BYTES, goal, limit, nid); - if (!p && limit) { + usage = memblock_alloc_try_nid(size, SMP_CACHE_BYTES, goal, limit, nid); + if (!usage && limit) { limit = 0; goto again; } - return p; + return usage; } -static void __init check_usemap_section_nr(int nid, unsigned long *usemap) +static void __init check_usemap_section_nr(int nid, + struct mem_section_usage *usage) { unsigned long usemap_snr, pgdat_snr; static unsigned long old_usemap_snr; @@ -352,7 +351,7 @@ static void __init check_usemap_section_nr(int nid, unsigned long *usemap) old_pgdat_snr = NR_MEM_SECTIONS; } - usemap_snr = pfn_to_section_nr(__pa(usemap) >> PAGE_SHIFT); + usemap_snr = pfn_to_section_nr(__pa(usage) >> PAGE_SHIFT); pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT); if (usemap_snr == pgdat_snr) return; @@ -380,14 +379,15 @@ static void __init check_usemap_section_nr(int nid, unsigned long *usemap) usemap_snr, pgdat_snr, nid); } #else -static unsigned long * __init +static struct mem_section_usage * __init sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, unsigned long size) { return memblock_alloc_node(size, SMP_CACHE_BYTES, pgdat->node_id); } -static void __init check_usemap_section_nr(int nid, unsigned long *usemap) +static void __init check_usemap_section_nr(int nid, + struct mem_section_usage *usage) { } #endif /* CONFIG_MEMORY_HOTREMOVE */ @@ -474,14 +474,13 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin, unsigned long pnum_end, unsigned long map_count) { - unsigned long pnum, usemap_longs, *usemap; + struct mem_section_usage *usage; + unsigned long pnum; struct page *map; - usemap_longs = BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS); - usemap = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nid), - usemap_size() * - map_count); - if (!usemap) { + usage = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nid), + mem_section_usage_size() * map_count); + if (!usage) { pr_err("%s: node[%d] usemap allocation failed", __func__, nid); goto failed; } @@ -497,9 +496,9 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin, pnum_begin = pnum; goto failed; } - check_usemap_section_nr(nid, usemap); - sparse_init_one_section(__nr_to_section(pnum), pnum, map, usemap); - usemap += usemap_longs; + check_usemap_section_nr(nid, usage); + sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage); + usage = (void *) usage + mem_section_usage_size(); } sparse_buffer_fini(); return; @@ -697,9 +696,9 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, struct vmem_altmap *altmap) { unsigned long section_nr = pfn_to_section_nr(start_pfn); + struct mem_section_usage *usage; struct mem_section *ms; struct page *memmap; - unsigned long *usemap; int ret; /* @@ -713,8 +712,8 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, memmap = kmalloc_section_memmap(section_nr, nid, altmap); if (!memmap) return -ENOMEM; - usemap = __kmalloc_section_usemap(); - if (!usemap) { + usage = kzalloc(mem_section_usage_size(), GFP_KERNEL); + if (!usage) { __kfree_section_memmap(memmap, altmap); return -ENOMEM; } @@ -732,11 +731,11 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, page_init_poison(memmap, sizeof(struct page) * PAGES_PER_SECTION); section_mark_present(ms); - sparse_init_one_section(ms, section_nr, memmap, usemap); + sparse_init_one_section(ms, section_nr, memmap, usage); out: if (ret < 0) { - kfree(usemap); + kfree(usage); __kfree_section_memmap(memmap, altmap); } return ret; @@ -772,20 +771,20 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages) } #endif -static void free_section_usemap(struct page *memmap, unsigned long *usemap, - struct vmem_altmap *altmap) +static void free_section_usage(struct page *memmap, + struct mem_section_usage *usage, struct vmem_altmap *altmap) { - struct page *usemap_page; + struct page *usage_page; - if (!usemap) + if (!usage) return; - usemap_page = virt_to_page(usemap); + usage_page = virt_to_page(usage); /* * Check to see if allocation came from hot-plug-add */ - if (PageSlab(usemap_page) || PageCompound(usemap_page)) { - kfree(usemap); + if (PageSlab(usage_page) || PageCompound(usage_page)) { + kfree(usage); if (memmap) __kfree_section_memmap(memmap, altmap); return; @@ -804,18 +803,18 @@ void sparse_remove_one_section(struct mem_section *ms, unsigned long map_offset, struct vmem_altmap *altmap) { struct page *memmap = NULL; - unsigned long *usemap = NULL; + struct mem_section_usage *usage = NULL; if (ms->section_mem_map) { - usemap = ms->pageblock_flags; + usage = ms->usage; memmap = sparse_decode_mem_map(ms->section_mem_map, __section_nr(ms)); ms->section_mem_map = 0; - ms->pageblock_flags = NULL; + ms->usage = NULL; } clear_hwpoisoned_pages(memmap + map_offset, PAGES_PER_SECTION - map_offset); - free_section_usemap(memmap, usemap, altmap); + free_section_usage(memmap, usage, altmap); } #endif /* CONFIG_MEMORY_HOTPLUG */
Towards enabling memory hotplug to track partial population of a section, introduce 'struct mem_section_usage'. A pointer to a 'struct mem_section_usage' instance replaces the existing pointer to a 'pageblock_flags' bitmap. Effectively it adds one more 'unsigned long' beyond the 'pageblock_flags' (usemap) allocation to house a new 'subsection_map' bitmap. The new bitmap enables the memory hot{plug,remove} implementation to act on incremental sub-divisions of a section. The default SUBSECTION_SHIFT is chosen to keep the 'subsection_map' no larger than a single 'unsigned long' on the major architectures. Alternatively an architecture can define ARCH_SUBSECTION_SHIFT to override the default PMD_SHIFT. Note that PowerPC needs to use ARCH_SUBSECTION_SHIFT to workaround PMD_SHIFT being a non-constant expression on PowerPC. The primary motivation for this functionality is to support platforms that mix "System RAM" and "Persistent Memory" within a single section, or multiple PMEM ranges with different mapping lifetimes within a single section. The section restriction for hotplug has caused an ongoing saga of hacks and bugs for devm_memremap_pages() users. Beyond the fixups to teach existing paths how to retrieve the 'usemap' from a section, and updates to usemap allocation path, there are no expected behavior changes. Cc: Michal Hocko <mhocko@suse.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Logan Gunthorpe <logang@deltatee.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- arch/powerpc/include/asm/sparsemem.h | 3 + include/linux/mmzone.h | 48 +++++++++++++++++++- mm/memory_hotplug.c | 18 ++++---- mm/page_alloc.c | 2 - mm/sparse.c | 81 +++++++++++++++++----------------- 5 files changed, 99 insertions(+), 53 deletions(-)