| Message ID | 20220318111709.60311-12-linmiaohe@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | A few cleanup and fixup patches for migration | expand |
Miaohe Lin <linmiaohe@huawei.com> writes: > When follow_page peeks a page, the page could be migrated and then be > offlined while it's still being used by the do_pages_stat_array(). > Use FOLL_GET to hold the page refcnt to fix this potential race. > > Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Acked-by: "Huang, Ying" <ying.huang@intel.com> > --- > mm/migrate.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index dbd91fbdb127..cd85ba0ab592 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1807,13 +1807,18 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, > goto set_status; > > /* FOLL_DUMP to ignore special (like zero) pages */ > - page = follow_page(vma, addr, FOLL_DUMP); > + page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); > > err = PTR_ERR(page); > if (IS_ERR(page)) > goto set_status; > > - err = page ? page_to_nid(page) : -ENOENT; > + if (page) { > + err = page_to_nid(page); > + put_page(page); > + } else { > + err = -ENOENT; > + } > set_status: > *status = err;
On Thu, Mar 17, 2022 at 10:42 PM Miaohe Lin <linmiaohe@huawei.com> wrote: > > When follow_page peeks a page, the page could be migrated and then be > offlined while it's still being used by the do_pages_stat_array(). > Use FOLL_GET to hold the page refcnt to fix this potential race. > > Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
diff --git a/mm/migrate.c b/mm/migrate.c index dbd91fbdb127..cd85ba0ab592 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1807,13 +1807,18 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, goto set_status; /* FOLL_DUMP to ignore special (like zero) pages */ - page = follow_page(vma, addr, FOLL_DUMP); + page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); err = PTR_ERR(page); if (IS_ERR(page)) goto set_status; - err = page ? page_to_nid(page) : -ENOENT; + if (page) { + err = page_to_nid(page); + put_page(page); + } else { + err = -ENOENT; + } set_status: *status = err;
When follow_page peeks a page, the page could be migrated and then be offlined while it's still being used by the do_pages_stat_array(). Use FOLL_GET to hold the page refcnt to fix this potential race. Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> --- mm/migrate.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)