On Mon, Aug 12, 2024 at 9:21 PM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
>
> On Mon, Aug 12, 2024 at 08:59:53PM +0800, Yafang Shao wrote:
> >
> > I don’t see any incompatibility in __alloc_pages_slowpath(). The
> > ~__GFP_DIRECT_RECLAIM flag only ensures that direct reclaim is not
> > performed, but it doesn’t prevent the allocation of pages from
> > ALLOC_MIN_RESERVE, correct?
> >
> > > and thus will lead to kernel crashes.
> >
> > Could you please explain in detail where this might lead to kernel crashes?
>
> Sorry, I misread your patch as doing what your subject says.
> A nestable noreclaim is probably fine, but please name it that way,
> as memalloc_nowait_{save,restore} implies a context version
> of GFP_NOWAIT.
There are already memalloc_noreclaim_{save,restore} which imply __GFP_MEMALLOC:
memalloc_noreclaim_save - Marks implicit __GFP_MEMALLOC scope.
That is why I name it memalloc_nowait_{save,restore}. GFP_NOWAIT has
the same meaning with ~__GFP_DIRECT_RECLAIM:
%GFP_NOWAIT is for kernel allocations that should not stall for direct
reclaim, start physical IO or use any filesystem callback.
--
Regards
Yafang
