On 30.04.20 21:32, Dave Hansen wrote: > On 4/30/20 11:12 AM, Christian Borntraeger wrote: >> On 29.04.20 18:07, Dave Hansen wrote: >>> On 4/28/20 3:50 PM, Claudio Imbrenda wrote: >>>> If a page is inaccesible and it is used for things like sendfile, then >>>> the content of the page is not always touched, and can be passed >>>> directly to a driver, causing issues. >>>> >>>> This patch fixes the issue by adding a call to arch_make_page_accessible >>>> in page_cache_pipe_buf_confirm; this fixes the issue. >>> I spent about 5 minutes putting together a patch: >>> >>> https://sr71.net/~dave/intel/accessible.patch >> You only set the page flag for compound pages. that of course leaves a big pile >> of pages marked a not accessible, thus explaining the sendto trace and all kind >> of other random traces. > > Ahh, nice catch! That does explain an oddity or two that I saw. > >> What do you see when you also do the SetPageAccessible(page); >> in the else page of prep_new_page (order == 0). >> (I do get > 10000 of these non compound page allocs just during boot). > > Yes, I see the same thing. > > I updated the patch and double-checked that it triggers properly with a > socket-based sendfile(). Do you have a calltrace?
