Messages in this thread | | | Date | Thu, 16 Apr 2020 16:59:00 +0200 | From | Claudio Imbrenda <> | Subject | Re: [PATCH v4 2/2] mm/gup/writeback: add callbacks for inaccessible pages |
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On Thu, 16 Apr 2020 07:20:48 -0700 Dave Hansen <dave.hansen@intel.com> 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. > > This means that host host has to write to the physical page and must > do arch_make_page_accessible() in the sys_write() path somewhere. > > There is a get_user_pages() in that path, but it's on the _source_ > buffer, not the ramfs page because the ramfs page is not mapped. > There's also no __test_set_page_writeback() because you can't write > back ramfs. > > 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
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