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 ym+jZmUf B1477pUqRrwAW8cMBart7uE9132ohH1J+KRqfL9nQLFPofY2YLzUqp+B40w5u7xbXwJEtn+bh4IeFzQvpulQLwRkk7P0duL/83wUjTvWYRh2OGokSLfBb3mJuhz7UkWHy8pE/IhXqzU+tOptP1NDXk3mlZf5w7uMf3tDnPgE9cGMMpq1qKcIAhXis2kZWvYrYyCovbcdHoKIcXbzlVbulafxazGCZmUuewcnTqFBdjJislEmLzQdNKKigcHdFdYMd8XZM219EACFrwEwOOUpu0rUN6hMLD6J5yQpmYxxhHSY9xZxINdzuEo8EgPIYs41qIP+lStooMP0UHvdAzBs7tfA1fmOCMSuhTCGN6ADUe3jGUYp9JFF2sxypZn37wJHrKjqFXb5Wx/w5uMlNoopBoSF/9i35dMkRrXEsZDHRSZVjUoUmTaizvPQa4v9+T0ANlwXdpt3C8LcBFiy8X6XxPpjsL9sTIhCD0nqS36ZBQz7x3ILjl4fHGY/85/Dr7ME8chSnHFDimpPlWGhBaHwswBj06ICXhi1DHP/2qYgIl556T9E= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jan 14, 2025 at 02:01:32PM +0100, David Hildenbrand wrote: > On 13.01.25 23:30, Yang Shi wrote: > > When creating private mapping for /dev/zero, the driver makes it an > > anonymous mapping by calling set_vma_anonymous(). But it just sets > > vm_ops to NULL, vm_file is still valid and vm_pgoff is also file offset. > > > > This is a special case and the VMA doesn't look like either anonymous VMA > > or file VMA. It confused other kernel subsystem, for example, khugepaged [1]. > > > > It seems pointless to keep such special case. Making private /dev/zero> > mapping a full anonymous mapping doesn't change the semantic of > > /dev/zero either. > > > > The user visible effect is the mapping entry shown in /proc//smaps > > and /proc//maps. > > > > Before the change: > > ffffb7190000-ffffb7590000 rw-p 00001000 00:06 8 /dev/zero > > > > After the change: > > ffffb6130000-ffffb6530000 rw-p 00000000 00:00 0 > > > > Hm, not sure about this. It's actually quite consistent to have that output > in smaps the way it is. You mapped a file at an offset, and it behaves like > an anonymous mapping apart from that. > > Not sure if the buggy khugepaged thing is a good indicator to warrant this > change. Yeah, this is a user-facing fundamental change that hides information and defies expectation so I mean - it's a no go really isn't it? I'd rather we _not_ make this anon though, because isn't life confusing enough David? I thought it was bad enough with 'anon, file and lol shmem' but 'lol lol also /dev/zero' is enough to make me want to frolick in the fields... > > -- > Cheers, > > David / dhildenb >