| Message ID | 20200122011647.13636-5-richardw.yang@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | cleanup on do_pages_move() | expand |
On 22.01.20 02:16, Wei Yang wrote: > When page is not queued for migration, there are two possible cases: > > * page already on the target node > * failed to add to migration queue > > Current code handle them differently, this leads to a behavior > inconsistency. > > Usually for each page's status, we just do store for once. While for the > page already on the target node, we might store the node information for > twice: > > * once when we found the page is on the target node > * second when moving the pages to target node successfully after above > action > > The reason is even we don't add the page to pagelist, but store_status() > does store in a range which still contains the page. > > This patch handles these two cases in the same way to reduce this > inconsistency and also make the code a little easier to read. > I'd rephrase to "mm/migrate.c: unify "not queued for migration" handling in do_pages_move() It can currently happen that we store the status of a page twice: * Once we detect that it is already on the target node * Once we moved a bunch of pages, and a page that's already on the target node is contained in the current interval. Let's simplify the code and always call do_move_pages_to_node() in case we did not queue a page for migration. Note that pages that are already on the target node are not added to the pagelist and are, therefore, ignored by do_move_pages_to_node() - there is no functional change. The status of such a page is now only stored once. " > Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> > Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/migrate.c | 16 ++++++++-------- > 1 file changed, 8 insertions(+), 8 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 80d2bba57265..591f2e5caed6 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1654,18 +1654,18 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, > err = add_page_for_migration(mm, addr, current_node, > &pagelist, flags & MPOL_MF_MOVE_ALL); > > - if (!err) { > - /* The page is already on the target node */ > - err = store_status(status, i, current_node, 1); > - if (err) > - goto out_flush; > - continue; > - } else if (err > 0) { > + if (err > 0) { > /* The page is successfully queued for migration */ > continue; > } > > - err = store_status(status, i, err, 1); > + /* > + * Two possible cases for err here: > + * == 0: page is already on the target node, then store > + * current_node to status > + * < 0: failed to add page to list, then store err to status > + */ I'd shorten that to /* * If the page is already on the target node (!err), store the node, * otherwise, store the err. */ > + err = store_status(status, i, err ? : current_node, 1); > if (err) > goto out_flush; > > Thanks! Reviewed-by: David Hildenbrand <david@redhat.com>
On Wed, Jan 29, 2020 at 11:13:23AM +0100, David Hildenbrand wrote: >On 22.01.20 02:16, Wei Yang wrote: >> When page is not queued for migration, there are two possible cases: >> >> * page already on the target node >> * failed to add to migration queue >> >> Current code handle them differently, this leads to a behavior >> inconsistency. >> >> Usually for each page's status, we just do store for once. While for the >> page already on the target node, we might store the node information for >> twice: >> >> * once when we found the page is on the target node >> * second when moving the pages to target node successfully after above >> action >> >> The reason is even we don't add the page to pagelist, but store_status() >> does store in a range which still contains the page. >> >> This patch handles these two cases in the same way to reduce this >> inconsistency and also make the code a little easier to read. >> > >I'd rephrase to > >"mm/migrate.c: unify "not queued for migration" handling in do_pages_move() > >It can currently happen that we store the status of a page twice: >* Once we detect that it is already on the target node >* Once we moved a bunch of pages, and a page that's already on the > target node is contained in the current interval. > >Let's simplify the code and always call do_move_pages_to_node() in >case we did not queue a page for migration. Note that pages that are >already on the target node are not added to the pagelist and are, >therefore, ignored by do_move_pages_to_node() - there is no functional >change. > >The status of such a page is now only stored once. >" > >> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> >> Acked-by: Michal Hocko <mhocko@suse.com> >> --- >> mm/migrate.c | 16 ++++++++-------- >> 1 file changed, 8 insertions(+), 8 deletions(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 80d2bba57265..591f2e5caed6 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1654,18 +1654,18 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, >> err = add_page_for_migration(mm, addr, current_node, >> &pagelist, flags & MPOL_MF_MOVE_ALL); >> >> - if (!err) { >> - /* The page is already on the target node */ >> - err = store_status(status, i, current_node, 1); >> - if (err) >> - goto out_flush; >> - continue; >> - } else if (err > 0) { >> + if (err > 0) { >> /* The page is successfully queued for migration */ >> continue; >> } >> >> - err = store_status(status, i, err, 1); >> + /* >> + * Two possible cases for err here: >> + * == 0: page is already on the target node, then store >> + * current_node to status >> + * < 0: failed to add page to list, then store err to status >> + */ > >I'd shorten that to > >/* > * If the page is already on the target node (!err), store the node, > * otherwise, store the err. >*/ > >> + err = store_status(status, i, err ? : current_node, 1); >> if (err) >> goto out_flush; >> >> > >Thanks! > >Reviewed-by: David Hildenbrand <david@redhat.com> > Yep, thanks. I would take this :-) >-- >Thanks, > >David / dhildenb
diff --git a/mm/migrate.c b/mm/migrate.c index 80d2bba57265..591f2e5caed6 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1654,18 +1654,18 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, err = add_page_for_migration(mm, addr, current_node, &pagelist, flags & MPOL_MF_MOVE_ALL); - if (!err) { - /* The page is already on the target node */ - err = store_status(status, i, current_node, 1); - if (err) - goto out_flush; - continue; - } else if (err > 0) { + if (err > 0) { /* The page is successfully queued for migration */ continue; } - err = store_status(status, i, err, 1); + /* + * Two possible cases for err here: + * == 0: page is already on the target node, then store + * current_node to status + * < 0: failed to add page to list, then store err to status + */ + err = store_status(status, i, err ? : current_node, 1); if (err) goto out_flush;
When page is not queued for migration, there are two possible cases: * page already on the target node * failed to add to migration queue Current code handle them differently, this leads to a behavior inconsistency. Usually for each page's status, we just do store for once. While for the page already on the target node, we might store the node information for twice: * once when we found the page is on the target node * second when moving the pages to target node successfully after above action The reason is even we don't add the page to pagelist, but store_status() does store in a range which still contains the page. This patch handles these two cases in the same way to reduce this inconsistency and also make the code a little easier to read. Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> --- mm/migrate.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)