linux-kernel - Re: [RESEND PATCH v5 3/4] mm/vmalloc: revert "mm/vmalloc.c: check VM_UNINITIALIZED flag in s_show instead of show_numa

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Date:	Mon, 16 Sep 2013 17:23:32 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	liwanp@...ux.vnet.ibm.com
CC:	kosaki.motohiro@...fujitsu.com, akpm@...ux-foundation.org,
	iamjoonsoo.kim@....com, rientjes@...gle.com,
	zhangyanfei@...fujitsu.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v5 3/4] mm/vmalloc: revert "mm/vmalloc.c: check
 VM_UNINITIALIZED flag in s_show instead of show_numa_info"

On 9/14/2013 7:45 PM, Wanpeng Li wrote:
> Changelog:
>  *v2 -> v3: revert commit d157a558 directly
> 
> The VM_UNINITIALIZED/VM_UNLIST flag introduced by commit f5252e00(mm: avoid
> null pointer access in vm_struct via /proc/vmallocinfo) is used to avoid
> accessing the pages field with unallocated page when show_numa_info() is
> called. This patch move the check just before show_numa_info in order that
> some messages still can be dumped via /proc/vmallocinfo. This patch revert 
> commit d157a558 (mm/vmalloc.c: check VM_UNINITIALIZED flag in s_show instead 
> of show_numa_info);

Both d157a558 and your patch don't explain why your one is better. Yes, some
messages _can_ be dumped. But why should we do so?

And No. __get_vm_area_node() doesn't use __GFP_ZERO for allocating vm_area_struct.
dumped partial dump is not only partial, but also may be garbage.

I wonder why we need to call setup_vmalloc_vm() _after_ insert_vmap_area.
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