Messages in this thread |  | | Date | Fri, 25 Jan 2013 09:07:47 -0600 | From | Seth Jennings <> | Subject | Re: [PATCHv2 1/9] staging: zsmalloc: add gfp flags to zs_create_pool |
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On 01/24/2013 07:33 PM, Minchan Kim wrote: > Hi Seth, frontswap guys > > On Tue, Jan 8, 2013 at 5:24 AM, Seth Jennings > <sjenning@linux.vnet.ibm.com> wrote: >> zs_create_pool() currently takes a gfp flags argument >> that is used when growing the memory pool. However >> it is not used in allocating the metadata for the pool >> itself. That is currently hardcoded to GFP_KERNEL. >> >> zswap calls zs_create_pool() at swapon time which is done >> in atomic context, resulting in a "might sleep" warning. > > I didn't review this all series, really sorry but totday I saw Nitin > added Acked-by so I'm afraid Greg might get it under my radar. I'm not > strong against but I would like know why we should call frontswap_init > under swap_lock? Is there special reason?
The call stack is:
SYSCALL_DEFINE2(swapon.. <-- swapon_mutex taken here enable_swap_info() <-- swap_lock taken here frontswap_init() __frontswap_init() zswap_frontswap_init() zs_create_pool()
It isn't entirely clear to me why frontswap_init() is called under lock. Then again, I'm not entirely sure what the swap_lock protects. There are no comments near the swap_lock definition to tell me.
I would guess that the intent is to block any writes to the swap device until frontswap_init() has completed.
Dan care to weigh in?
Seth
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