Messages in this thread | | | Subject | Re: [PATCH] mm: page_alloc: document kmemleak's non-blockable __GFP_NOFAIL case | From | Yang Shi <> | Date | Thu, 25 Jul 2019 10:21:08 -0700 |
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On 7/24/19 7:48 PM, Andrew Morton wrote: > On Sat, 13 Jul 2019 04:49:04 +0800 Yang Shi <yang.shi@linux.alibaba.com> 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Actually, this has been replaced by reverting the problematic commit.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?
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