| Message ID | 20210113052209.75531-2-songmuchun@bytedance.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix some bugs about HugeTLB code | expand |
On 13.01.21 06:22, Muchun Song wrote: > All pages isolated for the migration have an elevated reference count > and therefore seeing a reference count equal to 1 means that the last > user of the page has dropped the reference and the page has became > unused and there doesn't make much sense to migrate it anymore. This has > been done for regular pages and this patch does the same for hugetlb > pages. Although the likelyhood of the race is rather small for hugetlb > pages it makes sense the two code paths in sync. > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> > Acked-by: Yang Shi <shy828301@gmail.com> > Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/migrate.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 4385f2fb5d18..a6631c4eb6a6 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, > return -ENOSYS; > } > > + if (page_count(hpage) == 1) { > + /* page was freed from under us. So we are done. */ > + putback_active_hugepage(hpage); > + return MIGRATEPAGE_SUCCESS; > + } > + > new_hpage = get_new_page(hpage, private); > if (!new_hpage) > return -ENOMEM; > Happy to say that I now know understand what's going on here Reviewed-by: David Hildenbrand <david@redhat.com>
On Wed, Jan 13, 2021 at 01:22:04PM +0800, Muchun Song wrote: > diff --git a/mm/migrate.c b/mm/migrate.c > index 4385f2fb5d18..a6631c4eb6a6 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, > return -ENOSYS; > } > > + if (page_count(hpage) == 1) { > + /* page was freed from under us. So we are done. */ > + putback_active_hugepage(hpage); > + return MIGRATEPAGE_SUCCESS; > + } > + I was a bit puzzled as why we did not go to the "goto" block that already does this, but then I saw the put_new_page/new_hpage handlind further down. It could be re-arranged but out of scope, so: Reviewed-by: Oscar Salvador <osalvador@suse.de>
On Wed, Jan 13, 2021 at 6:57 PM Oscar Salvador <osalvador@suse.de> wrote: > > On Wed, Jan 13, 2021 at 01:22:04PM +0800, Muchun Song wrote: > > diff --git a/mm/migrate.c b/mm/migrate.c > > index 4385f2fb5d18..a6631c4eb6a6 100644 > > --- a/mm/migrate.c > > +++ b/mm/migrate.c > > @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, > > return -ENOSYS; > > } > > > > + if (page_count(hpage) == 1) { > > + /* page was freed from under us. So we are done. */ > > + putback_active_hugepage(hpage); > > + return MIGRATEPAGE_SUCCESS; > > + } > > + > > I was a bit puzzled as why we did not go to the "goto" block that already does > this, but then I saw the put_new_page/new_hpage handlind further down. > It could be re-arranged but out of scope, so: Agree. I also thought about this. :) > > Reviewed-by: Oscar Salvador <osalvador@suse.de> > Thanks. > > -- > Oscar Salvador > SUSE L3
diff --git a/mm/migrate.c b/mm/migrate.c index 4385f2fb5d18..a6631c4eb6a6 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, return -ENOSYS; } + if (page_count(hpage) == 1) { + /* page was freed from under us. So we are done. */ + putback_active_hugepage(hpage); + return MIGRATEPAGE_SUCCESS; + } + new_hpage = get_new_page(hpage, private); if (!new_hpage) return -ENOMEM;