Gregory Price <gregory.price@xxxxxxxxxxxx> writes: > On Wed, Jan 03, 2024 at 01:46:56PM +0800, Huang, Ying wrote: >> Gregory Price <gregory.price@xxxxxxxxxxxx> writes: >> > I'm specifically concerned about: >> > weighted_interleave_nid >> > alloc_pages_bulk_array_weighted_interleave >> > >> > I'm unsure whether kmalloc/kfree is safe (and non-offensive) in those >> > contexts. If kmalloc/kfree is safe fine, this problem is trivial. >> > >> > If not, there is no good solution to this without pre-allocating a >> > scratch area per-task. >> >> You need to audit whether it's safe for all callers. I guess that you >> need to allocate pages after calling, so you can use the same GFP flags >> here. >> > > After picking away i realized that this code is usually going to get > called during page fault handling - duh. So kmalloc is almost never > safe (or can fail), and we it's nasty to try to handle those errors. Why not just OOM for allocation failure? > Instead of doing that, I simply chose to implement the scratch space > in the mempolicy structure > > mempolicy->wil.scratch_weights[MAX_NUMNODES]. > > We eat an extra 1kb of memory in the mempolicy, but it gives us a safe > scratch space we can use any time the task is allocating memory, and > prevents the need for any fancy error handling. That seems like a > perfectly reasonable tradeoff. I don't think that this is a good idea. The weight array is temporary. -- Best Regards, Huang, Ying
