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    SubjectRe: [PATCH v6 2/5] mm/sparsemem: Defer the ms->section_mem_map clearing
    On Thu, Jun 28, 2018 at 02:28:54PM +0800, Baoquan He wrote:
    > In sparse_init(), if CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER=y, system
    > will allocate one continuous memory chunk for mem maps on one node and
    > populate the relevant page tables to map memory section one by one. If
    > fail to populate for a certain mem section, print warning and its
    > ->section_mem_map will be cleared to cancel the marking of being present.
    > Like this, the number of mem sections marked as present could become
    > less during sparse_init() execution.
    >
    > Here just defer the ms->section_mem_map clearing if failed to populate
    > its page tables until the last for_each_present_section_nr() loop. This
    > is in preparation for later optimizing the mem map allocation.
    >
    > Signed-off-by: Baoquan He <bhe@redhat.com>
    > Reviewed-by: Pavel Tatashin <pasha.tatashin@oracle.com>

    Looks good to me.

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

    > ---
    > mm/sparse-vmemmap.c | 4 ----
    > mm/sparse.c | 15 ++++++++-------
    > 2 files changed, 8 insertions(+), 11 deletions(-)
    >
    > diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
    > index bd0276d5f66b..68bb65b2d34d 100644
    > --- a/mm/sparse-vmemmap.c
    > +++ b/mm/sparse-vmemmap.c
    > @@ -292,18 +292,14 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
    > }
    >
    > for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
    > - struct mem_section *ms;
    > -
    > if (!present_section_nr(pnum))
    > continue;
    >
    > map_map[pnum] = sparse_mem_map_populate(pnum, nodeid, NULL);
    > if (map_map[pnum])
    > continue;
    > - ms = __nr_to_section(pnum);
    > pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
    > __func__);
    > - ms->section_mem_map = 0;
    > }
    >
    > if (vmemmap_buf_start) {
    > diff --git a/mm/sparse.c b/mm/sparse.c
    > index 6314303130b0..6a706093307d 100644
    > --- a/mm/sparse.c
    > +++ b/mm/sparse.c
    > @@ -441,17 +441,13 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
    >
    > /* fallback */
    > for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
    > - struct mem_section *ms;
    > -
    > if (!present_section_nr(pnum))
    > continue;
    > map_map[pnum] = sparse_mem_map_populate(pnum, nodeid, NULL);
    > if (map_map[pnum])
    > continue;
    > - ms = __nr_to_section(pnum);
    > pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
    > __func__);
    > - ms->section_mem_map = 0;
    > }
    > }
    > #endif /* !CONFIG_SPARSEMEM_VMEMMAP */
    > @@ -479,7 +475,6 @@ static struct page __init *sparse_early_mem_map_alloc(unsigned long pnum)
    >
    > pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
    > __func__);
    > - ms->section_mem_map = 0;
    > return NULL;
    > }
    > #endif
    > @@ -583,17 +578,23 @@ void __init sparse_init(void)
    > #endif
    >
    > for_each_present_section_nr(0, pnum) {
    > + struct mem_section *ms;
    > + ms = __nr_to_section(pnum);
    > usemap = usemap_map[pnum];
    > - if (!usemap)
    > + if (!usemap) {
    > + ms->section_mem_map = 0;
    > continue;
    > + }
    >
    > #ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
    > map = map_map[pnum];
    > #else
    > map = sparse_early_mem_map_alloc(pnum);
    > #endif
    > - if (!map)
    > + if (!map) {
    > + ms->section_mem_map = 0;
    > continue;
    > + }
    >
    > sparse_init_one_section(__nr_to_section(pnum), pnum, map,
    > usemap);
    > --
    > 2.13.6
    >

    --
    Oscar Salvador
    SUSE L3

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