On 4/16/20 7:59 AM, Claudio Imbrenda wrote: > On Thu, 16 Apr 2020 07:20:48 -0700 > Dave Hansen <dave.hansen@xxxxxxxxx> wrote: >> On 4/16/20 5:15 AM, Claudio Imbrenda wrote: >>>> I assumed that this was all anonymous-only so it's always dirty >>>> before writeback starts. >>> it could also be mmapped >> >> Let's say you have a mmap()'d ramfs file. Another process calls which >> doesn't have it mapped calls sys_write() and writes to the file. ... >> Where is the arch_make_page_accessible() in this case on the ramfs >> page? > > it's in the fault handler for the exception the CPU will get when > attempting to write the data to the protected page Ahh, so this is *just* intended to precede I/O done on the page, when a non-host entity is touching the memory? That seems inconsistent with the process_vm_readv/writev() paths which set FOLL_PIN on their pin_remote_user_pages() requests, but don't do I/O to the memory.
