Tiberiu A Georgescu <tiberiu.georgescu@xxxxxxxxxxx> writes: > Mentioning the current missing functionality of the pagemap, in case > someone stumbles upon unexpected behaviour. > > Signed-off-by: Tiberiu A Georgescu <tiberiu.georgescu@xxxxxxxxxxx> > Reviewed-by: Ivan Teterevkov <ivan.teterevkov@xxxxxxxxxxx> > Reviewed-by: Florian Schmidt <florian.schmidt@xxxxxxxxxxx> > Reviewed-by: Carl Waldspurger <carl.waldspurger@xxxxxxxxxxx> > Reviewed-by: Jonathan Davies <jonathan.davies@xxxxxxxxxxx> > --- > Documentation/admin-guide/mm/pagemap.rst | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst > index fb578fbbb76c..627f3832b3a2 100644 > --- a/Documentation/admin-guide/mm/pagemap.rst > +++ b/Documentation/admin-guide/mm/pagemap.rst > @@ -207,3 +207,9 @@ Before Linux 3.11 pagemap bits 55-60 were used for "page-shift" (which is > always 12 at most architectures). Since Linux 3.11 their meaning changes > after first clear of soft-dirty bits. Since Linux 4.2 they are used for > flags unconditionally. > + > +Note that the page table entries for swappable and non-syncable pages are > +cleared when those pages are zapped or swapped out. This makes information > +about the page disappear from the pagemap. The location of the swapped > +page can still be retrieved from the page cache, but flags like SOFT_DIRTY > +and UFFD_WP are lost irretrievably. Thanks for the patch, please accept my apologies for taking to long to look at it. The change seems OK to me, but I think that the memory-management developers should get a chance to at least look at it before I merge it. Could I ask you to submit, including the linux-mm list on CC? Thanks, jon
