On Tue, Aug 24, 2021 at 05:23:04PM +0000, Edgecombe, Rick P wrote: > On Tue, 2021-08-24 at 19:54 +0300, Mike Rapoport wrote: > > On Tue, Aug 24, 2021 at 04:38:03PM +0000, Edgecombe, Rick P wrote: > > > On Tue, 2021-08-24 at 16:02 +0300, Mike Rapoport wrote: > > > > > We probably want to exclude GFP_ATOMIC before calling into CPA > > > > > unless > > > > > debug page alloc is on, because it may need to split and sleep > > > > > for > > > > > the > > > > > allocation. There is a page table allocation with GFP_ATOMIC > > > > > passed > > > > > actually. > > > > > > > > Looking at the callers of alloc_low_pages() it seems that > > > > GFP_ATOMIC > > > > there > > > > is stale... > > > > > > Well two actually, there is also spp_getpage(). I tried to > > > determine if > > > that was also stale but wasn't confident. There were a lot of paths > > > in. > > > > > > It's also used at init and during memory hotplug, so I really doubt > > it > > needs GFP_ATOMIC. > > Pretty sure it gets called after init by at least something besides > hotplug. I saw it during debugging with a little sanitizer I built to > find any unprotected page tables missed. Something tweaking the fixmap > IIRC. Did you look at the set_fixmap_() and set_pte_vaddr() family of > functions? Now whether any of them actually need GFP_ATOMIC, I am less > sure. There were a fair amount of drivers to analyze. Oh, I've missed set_pte_vaddr(). I still doubt anything that uses those two would need GFP_ATOMIC, but it's surely way harder to analyze. -- Sincerely yours, Mike.
