On Sat, Oct 2, 2021 at 10:09 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Thu, Sep 30, 2021 at 10:39:14AM -0700, Yang Shi wrote: > > On Thu, Sep 30, 2021 at 9:49 AM Hugh Dickins <hughd@xxxxxxxxxx> wrote: > > > I assume you're thinking of one of the fuzzer blkdev ones: > > > https://lore.kernel.org/linux-mm/CACkBjsbtF_peC7N_4mRfHML_BeiPe+O9DahTfr84puSG_J9rcQ@xxxxxxxxxxxxxx/ > > > or > > > https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@xxxxxxxxxxxxxx/ > > > > > > I haven't started on those ones yet: yes, I imagine one or both of those > > > will need a further fix (S_ISREG() check somewhere if we're lucky; but > > > could well be nastier); but for the bug in this thread, I expect > > > > Makes sense to me. We should be able to check S_ISREG() in khugepaged, > > if it is not a regular file, just bail out. Sounds not that nasty to > > me AFAIU. > > I don't see why we should have an S_ISREG() check. I agree it's not the > intended usecase, but it ought to work fine. Unless there's something > I'm missing? Check out this bug report: https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@xxxxxxxxxxxxxx/ and the patch from me: https://lore.kernel.org/linux-mm/20210917205731.262693-1-shy828301@xxxxxxxxx/ I don't think we handle buffers correctly for file THP, right? My patch is ad hoc, so I thought Hugh's suggestion makes some sense to me. Why do we have THP collapsed for unintended usecase in the first place?
