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@xxxxxxxxxxxxxxxxxx> 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>