On 7/24/19 7:48 PM, Andrew Morton wrote:
On Sat, 13 Jul 2019 04:49:04 +0800 Yang Shi <[email protected]> wrote:When running ltp's oom test with kmemleak enabled, the below warning was triggerred since kernel detects __GFP_NOFAIL & ~__GFP_DIRECT_RECLAIM is passed in: ... The mempool_alloc_slab() clears __GFP_DIRECT_RECLAIM, kmemleak has __GFP_NOFAIL set all the time due to commit d9570ee3bd1d4f20ce63485f5ef05663866fe6c0 ("kmemleak: allow to coexist with fault injection"). The fault-injection would not try to fail slab or page allocation if __GFP_NOFAIL is used and that commit tries to turn off fault injection for kmemleak allocation. Although __GFP_NOFAIL doesn't guarantee no failure for all the cases (i.e. non-blockable allocation may fail), it still makes sense to the most cases. Kmemleak is also a debugging tool, so it sounds not worth changing the behavior. It also meaks sense to keep the warning, so just document the special case in the comment. ... --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4531,8 +4531,14 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask) */ if (gfp_mask & __GFP_NOFAIL) { /* - * All existing users of the __GFP_NOFAIL are blockable, so warn - * of any new users that actually require GFP_NOWAIT + * The users of the __GFP_NOFAIL are expected be blockable, + * and this is true for the most cases except for kmemleak. + * The kmemleak pass in __GFP_NOFAIL to skip fault injection, + * however kmemleak may allocate object at some non-blockable + * context to trigger this warning. + * + * Keep this warning since it is still useful for the most + * normal cases. */Comment has rather a lot of typos. I'd normally fix them but I think I'll duck this patch until the kmemleak situation is addressed, so we can add a kmemleakless long-term comment, if desired.
Actually, this has been replaced by reverting the problematic commit. And, the patch has been in -mm tree. Please see: revert-kmemleak-allow-to-coexist-with-fault-injection.patch
I think we would like to have this merged in 5.3-rc1 or rc2?
