On Thu, Oct 07, 2021 at 09:27:49AM +1100, Dave Chinner wrote: > On Wed, Oct 06, 2021 at 08:43:27AM -0700, Darrick J. Wong wrote: > > On Wed, Oct 06, 2021 at 04:14:43PM +0800, Hao Sun wrote: > > > Hello, > > > > > > When using Healer to fuzz the latest Linux kernel, the following crash > > > was triggered. > > > > > > HEAD commit: 0513e464f900 Merge tag 'perf-tools-fixes-for-v5.15-2021-09-27' > > > git tree: upstream > > > console output: > > > https://drive.google.com/file/d/1vm5fDM220kkghoiGa3Aw_Prl4O_pqAXF/view?usp=sharing > > > kernel config: https://drive.google.com/file/d/1Jqhc4DpCVE8X7d-XBdQnrMoQzifTG5ho/view?usp=sharing > > > > > > Sorry, I don't have a reproducer for this crash, hope the symbolized > > > report can help. > > > If you fix this issue, please add the following tag to the commit: > > > Reported-by: Hao Sun <sunhao.th@xxxxxxxxx> > > > > So figure out how to fix the problem and send a patch. You don't get to > > hand out fixit tasks like you're some kind of manager for people you > > don't employ. > > I fully agree with this Darrick but, OTOH, the cynical, jaded > engineer in me says "I don't think people that run bots and > copy/paste their output to mailing lists have the capability to fix > the problems the bots find." They gotta learn to level up (or leave us alone) somehow... > Quite frankly, it's even more of a waste of our time trying to > review crap patches and make suggestions to fix it and then going > around the review loop 15 times getting nowhere like we have in teh > past. > > So, kvmalloc() sucks dogs balls, as I pointed out in this recent > patch in the intent whiteouts series: > > https://lore.kernel.org/linux-xfs/20210902095927.911100-8-david@xxxxxxxxxxxxx/ > > Because of the crap implementation of kvmalloc(), we can't just pass > __GFP_NOFAIL because that will cause it to try to run > kmalloc_node(__GFP_NORETRY | __GFP_NOFAIL) and that will cause heads > to go all explodey. Not to mention that kvmalloc won't even allow > GFP_NOFS to be passed and still actually do the vmalloc() fallback. > > So, basically, we've got to go back to doing an open coded kvmalloc > loop here that cannot fail. Because kvmalloc can fail and we can't > tell it that it must succeed or die trying. > > That's what the above patch does - gets rid of the garbage kvmalloc > direct reclaim -> memory compaction behaviour, and wraps it in a > loop so that the fail-fast memory allocation semantics it uses does > not end up in a shadow buffer allocation failure. > > So, yeah, I've already fixed this in my trees.... Er, do you want me to queue that patch for 5.17? I had assumed it was only really needed for allison's patches, but I don't mind pushing it in sooner. --D > Cheers, > > Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx
