On Tue, Apr 30, 2024 at 03:28:22PM +1000, Dave Chinner wrote: > This patchset is the followup to the comment I made earlier today: > > https://lore.kernel.org/linux-xfs/ZjAyIWUzDipofHFJ@xxxxxxxxxxxxxxxxxxx/ > > Tl;dr: Memory allocations that are done inside the public memory > allocation API need to obey the reclaim recursion constraints placed > on the allocation by the original caller, including the "don't track > recursion for this allocation" case defined by __GFP_NOLOCKDEP. > > These nested allocations are generally in debug code that is > tracking something about the allocation (kmemleak, KASAN, etc) and > so are allocating private kernel objects that only that debug system > will use. > > Neither the page-owner code nor the stack depot code get this right. > They also also clear GFP_ZONEMASK as a separate operation, which is > completely redundant because the constraint filter applied > immediately after guarantees that GFP_ZONEMASK bits are cleared. > > kmemleak gets this filtering right. It preserves the allocation > constraints for deadlock prevention and clears all other context > flags whilst also ensuring that the nested allocation will fail > quickly, silently and without depleting emergency kernel reserves if > there is no memory available. > > This can be made much more robust, immune to whack-a-mole games and > the code greatly simplified by lifting gfp_kmemleak_mask() to > include/linux/gfp.h and using that everywhere. Also document it so > that there is no excuse for not knowing about it when writing new > debug code that nests allocations. > > Tested with lockdep, KASAN + page_owner=on and kmemleak=on over > multiple fstests runs with XFS. Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Thanks! -- Oscar Salvador SUSE Labs
