On Sat, Sep 18, 2021 at 1:20 PM Barry Song <21cnbao@xxxxxxxxx> wrote: > > On Sat, Sep 18, 2021 at 12:08 AM Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote: > > > > Since the head vmemmap page frame associated with each HugeTLB page is > > reused, we should hide the PG_head flag of tail struct page from the > > user. Add a tese case to check whether it is work properly. > > > > TBH, I am a bit confused. I was thinking about some kernel unit tests to make > sure those kernel APIs touched by this patchset are still working as before. > This userspace test, while certainly useful for checking the content of page > frames as expected, doesn't directly prove things haven't changed. > > In patch 1/4, a couple of APIs have the fixup for the fake head issue. > Do you think a test like the below would be more sensible? > 1. alloc 2MB hugeTLB It is done in main(). > 2. get each page frame > 3. apply those APIs in each page frame > 4. Those APIs work completely the same as before. Reading the flags of a page by /proc/kpageflags is done in stable_page_flags(), which has invoked PageHead(), PageTail(), PageCompound() and compound_head(). If those APIs work properly, the head page must have 15 and 17 bits set. And tail pages must have 16 and 17 bits set but 15 unset. So I think check_page_flags() has done the step 2 to 4. What do you think? Thanks.
