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    DateFri, 9 May 2008 15:39:10 +0900
    FromKAMEZAWA Hiroyuki <>
    SubjectRe: [PATCH] memory_hotplug: always initialize pageblock bitmap.
    On Fri, 9 May 2008 08:06:09 +0200
    Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
    
    > From: Heiko Carstens <heiko.carstens@de.ibm.com>
    > 
    > Trying to online a new memory section that was added via memory hotplug
    > sometimes results in crashes when the new pages are added via
    > __free_page. Reason for that is that the pageblock bitmap isn't
    > initialized and hence contains random stuff.
    
    Hmm, curious. In my understanding, memmap_init_zone() initializes it.
    
     __add_pages()
    	-> __add_section()
    		-> sparse-add_one_section() // allocate usemap
    		-> __add_zone()
    			-> memmap_init_zone() // reset pageblock's bitmap 
    Can't memmap_init_zone() does proper initialization ?
    ........................
    Ah, ok. I see. grow_zone_span() is not called at __add_zone(), then,
    memmap_init_zone() doesn't initialize usemap because memmap is not in zone's
    range.
    Recently, I added a check "zone's start_pfn < pfn < zone's end"
    to memmap_init_zone()'s usemap initialization for !SPARSEMEM case bug FIX.
    (and I think the fix itself is sane.)
    
    How about calling grow_pgdat_span()/grow_zone_span() from __add_zone() ?
    
    Thanks,
    -Kame
    
    
    
    
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