From: Baoquan He <bhe@xxxxxxxxxx> Subject: mm/sparsemem.c: defer the ms->section_mem_map clearing 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. [akpm@xxxxxxxxxxxxxxxxxxxx: remove now-unused local `ms', per Oscar] Link: http://lkml.kernel.org/r/20180228032657.32385-3-bhe@xxxxxxxxxx Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> Acked-by: Dave Hansen <dave.hansen@xxxxxxxxx> Reviewed-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Cc: Pasha Tatashin <Pavel.Tatashin@xxxxxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Pankaj Gupta <pagupta@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/sparse-vmemmap.c | 4 ---- mm/sparse.c | 12 ++++++++---- 2 files changed, 8 insertions(+), 8 deletions(-) --- a/mm/sparse.c~mm-sparsemem-defer-the-ms-section_mem_map-clearing +++ a/mm/sparse.c @@ -446,7 +446,6 @@ void __init sparse_mem_maps_populate_nod 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 */ @@ -474,7 +473,6 @@ static struct page __init *sparse_early_ pr_err("%s: sparsemem memory map backing failed some memory will not be available\n", __func__); - ms->section_mem_map = 0; return NULL; } #endif @@ -578,17 +576,23 @@ 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); --- a/mm/sparse-vmemmap.c~mm-sparsemem-defer-the-ms-section_mem_map-clearing +++ a/mm/sparse-vmemmap.c @@ -292,18 +292,14 @@ void __init sparse_mem_maps_populate_nod } 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) { _
