Oscar Salvador <osalva...@suse.de> writes: > Since [1], shrink_{zone,node}_span work on PAGES_PER_SUBSECTION granularity. > The problem is that deactivation of the section occurs later on in > sparse_remove_section, so pfn_valid()->pfn_section_valid() will always return > true before we deactivate the {sub}section.
Can you explain this more? The patch doesn't update section_mem_map update sequence. So what changed? What is the problem in finding pfn_valid() return true there? > > I spotted this during hotplug hotremove tests, there I always saw that > spanned_pages was, at least, left with PAGES_PER_SECTION, even if we > removed all memory linked to that zone. > > Fix this by decoupling section_deactivate from sparse_remove_section, and > re-order the function calls. > > Now, __remove_section will: > > 1) deactivate section > 2) shrink {zone,node}'s pages > 3) remove section > > [1] https://patchwork.kernel.org/patch/11003467/ > > Fixes: mmotm ("mm/hotplug: prepare shrink_{zone, pgdat}_span for sub-section > removal") > Signed-off-by: Oscar Salvador <osalva...@suse.de> > --- > include/linux/memory_hotplug.h | 7 ++-- > mm/memory_hotplug.c | 6 +++- > mm/sparse.c | 77 > +++++++++++++++++++++++++++++------------- > 3 files changed, 62 insertions(+), 28 deletions(-) > > diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h > index f46ea71b4ffd..d2eb917aad5f 100644 > --- a/include/linux/memory_hotplug.h > +++ b/include/linux/memory_hotplug.h > @@ -348,9 +348,10 @@ extern void move_pfn_range_to_zone(struct zone *zone, > unsigned long start_pfn, > extern bool is_memblock_offlined(struct memory_block *mem); > extern int sparse_add_section(int nid, unsigned long pfn, > unsigned long nr_pages, struct vmem_altmap *altmap); > -extern void sparse_remove_section(struct mem_section *ms, > - unsigned long pfn, unsigned long nr_pages, > - unsigned long map_offset, struct vmem_altmap *altmap); > +int sparse_deactivate_section(unsigned long pfn, unsigned long nr_pages); > +void sparse_remove_section(unsigned long pfn, unsigned long nr_pages, > + unsigned long map_offset, struct vmem_altmap > *altmap, > + int section_empty); > extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map, > unsigned long pnum); > extern bool allow_online_pfn_range(int nid, unsigned long pfn, unsigned long > nr_pages, > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index b9ba5b85f9f7..03d535eee60d 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -517,12 +517,16 @@ static void __remove_section(struct zone *zone, > unsigned long pfn, > struct vmem_altmap *altmap) > { > struct mem_section *ms = __nr_to_section(pfn_to_section_nr(pfn)); > + int ret; > > if (WARN_ON_ONCE(!valid_section(ms))) > return; > > + ret = sparse_deactivate_section(pfn, nr_pages); > __remove_zone(zone, pfn, nr_pages); > - sparse_remove_section(ms, pfn, nr_pages, map_offset, altmap); > + if (ret >= 0) > + sparse_remove_section(pfn, nr_pages, map_offset, altmap, > + ret); > } > > /** > diff --git a/mm/sparse.c b/mm/sparse.c > index 1e224149aab6..d4953ee1d087 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -732,16 +732,47 @@ static void free_map_bootmem(struct page *memmap) > } > #endif /* CONFIG_SPARSEMEM_VMEMMAP */ > > -static void section_deactivate(unsigned long pfn, unsigned long nr_pages, > - struct vmem_altmap *altmap) > +static void section_remove(unsigned long pfn, unsigned long nr_pages, > + struct vmem_altmap *altmap, int section_empty) > +{ > + struct mem_section *ms = __pfn_to_section(pfn); > + bool section_early = early_section(ms); > + struct page *memmap = NULL; > + > + if (section_empty) { > + unsigned long section_nr = pfn_to_section_nr(pfn); > + > + if (!section_early) { > + kfree(ms->usage); > + ms->usage = NULL; > + } > + memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr); > + ms->section_mem_map = sparse_encode_mem_map(NULL, section_nr); > + } > + > + if (section_early && memmap) > + free_map_bootmem(memmap); > + else > + depopulate_section_memmap(pfn, nr_pages, altmap); > +} > + > +/** > + * section_deactivate: Deactivate a {sub}section. > + * > + * Return: > + * * -1 - {sub}section has already been deactivated. > + * * 0 - Section is not empty > + * * 1 - Section is empty > + */ > + > +static int section_deactivate(unsigned long pfn, unsigned long nr_pages) > { > DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 }; > DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 }; > struct mem_section *ms = __pfn_to_section(pfn); > - bool section_is_early = early_section(ms); > - struct page *memmap = NULL; > unsigned long *subsection_map = ms->usage > ? &ms->usage->subsection_map[0] : NULL; > + int section_empty = 0; > > subsection_mask_set(map, pfn, nr_pages); > if (subsection_map) > @@ -750,7 +781,7 @@ static void section_deactivate(unsigned long pfn, > unsigned long nr_pages, > if (WARN(!subsection_map || !bitmap_equal(tmp, map, > SUBSECTIONS_PER_SECTION), > "section already deactivated (%#lx + %ld)\n", > pfn, nr_pages)) > - return; > + return -1; > > /* > * There are 3 cases to handle across two configurations > @@ -770,21 +801,10 @@ static void section_deactivate(unsigned long pfn, > unsigned long nr_pages, > * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified > */ > bitmap_xor(subsection_map, map, subsection_map, > SUBSECTIONS_PER_SECTION); > - if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) { > - unsigned long section_nr = pfn_to_section_nr(pfn); > - > - if (!section_is_early) { > - kfree(ms->usage); > - ms->usage = NULL; > - } > - memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr); > - ms->section_mem_map = sparse_encode_mem_map(NULL, section_nr); > - } > + if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) > + section_empty = 1; > > - if (section_is_early && memmap) > - free_map_bootmem(memmap); > - else > - depopulate_section_memmap(pfn, nr_pages, altmap); > + return section_empty; > } > > static struct page * __meminit section_activate(int nid, unsigned long pfn, > @@ -834,7 +854,11 @@ static struct page * __meminit section_activate(int nid, > unsigned long pfn, > > memmap = populate_section_memmap(pfn, nr_pages, nid, altmap); > if (!memmap) { > - section_deactivate(pfn, nr_pages, altmap); > + int ret; > + > + ret = section_deactivate(pfn, nr_pages); > + if (ret >= 0) > + section_remove(pfn, nr_pages, altmap, ret); > return ERR_PTR(-ENOMEM); > } > > @@ -919,12 +943,17 @@ static inline void clear_hwpoisoned_pages(struct page > *memmap, int nr_pages) > } > #endif > > -void sparse_remove_section(struct mem_section *ms, unsigned long pfn, > - unsigned long nr_pages, unsigned long map_offset, > - struct vmem_altmap *altmap) > +int sparse_deactivate_section(unsigned long pfn, unsigned long nr_pages) > +{ > + return section_deactivate(pfn, nr_pages); > +} > + > +void sparse_remove_section(unsigned long pfn, unsigned long nr_pages, > + unsigned long map_offset, struct vmem_altmap *altmap, > + int section_empty) > { > clear_hwpoisoned_pages(pfn_to_page(pfn) + map_offset, > nr_pages - map_offset); > - section_deactivate(pfn, nr_pages, altmap); > + section_remove(pfn, nr_pages, altmap, section_empty); > } > #endif /* CONFIG_MEMORY_HOTPLUG */ > -- > 2.12.3