----- Original Message -----
> On Sun 26-08-18 15:47:52, Michael Kerrisk wrote:
> > Hello Jan,
> >
> > On 08/24/2018 02:27 PM, Jan Stancek wrote:
> > > Since the rework done in a49bd4d71637 ("mm, numa: rework do_pages_move"),
> > > move_pages() can return also positive value.
> > >
> > > Signed-off-by: Jan Stancek <jstancek@xxxxxxxxxx>
> > > ---
> > > man2/move_pages.2 | 6 ++++--
> > > 1 file changed, 4 insertions(+), 2 deletions(-)
> > >
> > > https://github.com/linux-test-project/ltp/issues/388
> > >
> > > diff --git a/man2/move_pages.2 b/man2/move_pages.2
> > > index f2c4f7f7a269..35cf6de1ba78 100644
> > > --- a/man2/move_pages.2
> > > +++ b/man2/move_pages.2
> > > @@ -157,9 +157,11 @@ The page is not present.
> > > .B -ENOMEM
> > > Unable to allocate memory on target node.
> > > .SH RETURN VALUE
> > > -On success
> > > +On success (since 4.17)
> > > .BR move_pages ()
> > > -returns zero.
> > > +returns the number of pages that could not be moved
> > > +(i.e., a return of zero means that all pages were successfully moved,
> > > +older kernels return 0).
> > > .\" FIXME . Is the following quite true: does the wrapper in numactl
> > > .\" do the right thing?
> > > On error, it returns \-1, and sets
> >
> > The wording here seems a bit confusing, because the detail about
> > older kernel behavior is hidden in a parenthetical aside. Can you
> > confirm what I understand:
> >
> > [[
> > Before Linux 4.17, move_pages() always returned 0 on success.
> > [But, what is the return value if not all of the pages could
> > be moved? Is it 0 or -1?]
>
> Please refer to the changelog of the commit. The failure semantic was
> quite hazy. Some errors were simply not reported. But in general there
> was -1 on failure and 0 on success (whatever the later means). One would
> have to check for status of each page to tell.
Could we define 'success' as "status array has been populated"?
>
> > Since Linux, a successful call to move_pages() returns the number
> > of pages that could not be moved (i.e., a return of zero means that
> > all pages were successfully moved, older kernels return 0).
> > ]]
> >
> > If that's correct, then I think the new text should read more
> > like that, withe open question answered.
Would this work?
[[
Before Linux 4.17, return value of 0 (success) meant that result
of the move (per page) is stored in status array.
Since Linux 4.17, a successful call to move_pages() returns the number
of pages that could not be moved (i.e., a return of zero means that
all pages were successfully moved), and populates status array.
]]
Regards,
Jan
