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SubjectRe: [PATCH v9 07/12] mm/sparsemem: Prepare for sub-section ranges
On Wed, Jun 05, 2019 at 02:58:37PM -0700, Dan Williams wrote:
> Prepare the memory hot-{add,remove} paths for handling sub-section
> ranges by plumbing the starting page frame and number of pages being
> handled through arch_{add,remove}_memory() to
> sparse_{add,remove}_one_section().
>
> This is simply plumbing, small cleanups, and some identifier renames. No
> intended functional 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>
> Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> include/linux/memory_hotplug.h | 5 +-
> mm/memory_hotplug.c | 114 +++++++++++++++++++++++++---------------
> mm/sparse.c | 15 ++---
> 3 files changed, 81 insertions(+), 53 deletions(-)
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 79e0add6a597..3ab0282b4fe5 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -348,9 +348,10 @@ extern int add_memory_resource(int nid, struct resource *resource);
> extern void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
> unsigned long nr_pages, struct vmem_altmap *altmap);
> extern bool is_memblock_offlined(struct memory_block *mem);
> -extern int sparse_add_one_section(int nid, unsigned long start_pfn,
> - struct vmem_altmap *altmap);
> +extern int sparse_add_section(int nid, unsigned long pfn,
> + unsigned long nr_pages, struct vmem_altmap *altmap);
> extern void sparse_remove_one_section(struct mem_section *ms,
> + unsigned long pfn, unsigned long nr_pages,
> unsigned long map_offset, struct vmem_altmap *altmap);
> extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map,
> unsigned long pnum);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 4b882c57781a..399bf78bccc5 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -252,51 +252,84 @@ void __init register_page_bootmem_info_node(struct pglist_data *pgdat)
> }
> #endif /* CONFIG_HAVE_BOOTMEM_INFO_NODE */
>
> -static int __meminit __add_section(int nid, unsigned long phys_start_pfn,
> - struct vmem_altmap *altmap)
> +static int __meminit __add_section(int nid, unsigned long pfn,
> + unsigned long nr_pages, struct vmem_altmap *altmap)
> {
> int ret;
>
> - if (pfn_valid(phys_start_pfn))
> + if (pfn_valid(pfn))
> return -EEXIST;
>
> - ret = sparse_add_one_section(nid, phys_start_pfn, altmap);
> + ret = sparse_add_section(nid, pfn, nr_pages, altmap);
> return ret < 0 ? ret : 0;
> }
>
> +static int check_pfn_span(unsigned long pfn, unsigned long nr_pages,
> + const char *reason)
> +{
> + /*
> + * Disallow all operations smaller than a sub-section and only
> + * allow operations smaller than a section for
> + * SPARSEMEM_VMEMMAP. Note that check_hotplug_memory_range()
> + * enforces a larger memory_block_size_bytes() granularity for
> + * memory that will be marked online, so this check should only
> + * fire for direct arch_{add,remove}_memory() users outside of
> + * add_memory_resource().
> + */
> + unsigned long min_align;
> +
> + if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
> + min_align = PAGES_PER_SUBSECTION;
> + else
> + min_align = PAGES_PER_SECTION;
> + if (!IS_ALIGNED(pfn, min_align)
> + || !IS_ALIGNED(nr_pages, min_align)) {
> + WARN(1, "Misaligned __%s_pages start: %#lx end: #%lx\n",
> + reason, pfn, pfn + nr_pages - 1);
> + return -EINVAL;
> + }
> + return 0;
> +}


This caught my eye.
Back in patch#4 "Convert kmalloc_section_memmap() to populate_section_memmap()",
you placed a mis-usage check for !CONFIG_SPARSEMEM_VMEMMAP in
populate_section_memmap().

populate_section_memmap() gets called from sparse_add_one_section(), which means
that we should have passed this check, otherwise we cannot go further and call
__add_section().

So, unless I am missing something it seems to me that the check from patch#4 could go?
And I think the same applies to depopulate_section_memmap()?

Besides that, it looks good to me:

Reviewed-by: Oscar Salvador <osalvador@suse.de>

--
Oscar Salvador
SUSE L3

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