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.
> 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.
>
> How does that sound?
OK, with me.
--
Michal Hocko
SUSE Labs
