| Message ID | 20191004073755.3228-1-miles.chen@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/page_owner: fix incorrect looping in __set_page_owner_handle() | expand |
On 10/4/19 9:37 AM, Miles Chen wrote: > In __set_page_owner_handle(), we should loop over page > [0...(1 << order) - 1] and setup their page_owner structures. > > Currently, __set_page_owner_handle() update page_ext at the end of > the loop, sets the page_owner of (page + 0) twice and > misses the page_owner of (page + (1 << order) - 1). > > Fix it by updating the page_ext at the start of the loop. > > In i == 0 case: > for (i = 0; i < (1 << order); i++) { > page_owner = get_page_owner(page_ext); <- page_ext belongs to page + 0 > ... > page_ext = lookup_page_ext(page + i); <- lookup_page_ext(page + 0) > } > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Vlastimil Babka <vbabka@suse.cz> > Cc: Michal Hocko <mhocko@suse.com> > Signed-off-by: Miles Chen <miles.chen@mediatek.com> > Fixes: 7e2f2a0cd17c ("mm, page_owner: record page owner for each subpage") Thanks. Kirill spotted it earlier and there's a fix pending: https://lore.kernel.org/linux-mm/20190930122916.14969-2-vbabka@suse.cz/ > --- > mm/page_owner.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index dee931184788..110c3e1987f2 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -178,6 +178,7 @@ static inline void __set_page_owner_handle(struct page *page, > int i; > > for (i = 0; i < (1 << order); i++) { > + page_ext = lookup_page_ext(page + i); > page_owner = get_page_owner(page_ext); > page_owner->handle = handle; > page_owner->order = order; > @@ -185,8 +186,6 @@ static inline void __set_page_owner_handle(struct page *page, > page_owner->last_migrate_reason = -1; > __set_bit(PAGE_EXT_OWNER, &page_ext->flags); > __set_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags); > - > - page_ext = lookup_page_ext(page + i); > } > } > >
On Fri, 2019-10-04 at 09:57 +0200, Vlastimil Babka wrote: > On 10/4/19 9:37 AM, Miles Chen wrote: > > In __set_page_owner_handle(), we should loop over page > > [0...(1 << order) - 1] and setup their page_owner structures. > > > > Currently, __set_page_owner_handle() update page_ext at the end of > > the loop, sets the page_owner of (page + 0) twice and > > misses the page_owner of (page + (1 << order) - 1). > > > > Fix it by updating the page_ext at the start of the loop. > > > > In i == 0 case: > > for (i = 0; i < (1 << order); i++) { > > page_owner = get_page_owner(page_ext); <- page_ext belongs to page + 0 > > ... > > page_ext = lookup_page_ext(page + i); <- lookup_page_ext(page + 0) > > } > > > > Cc: Andrew Morton <akpm@linux-foundation.org> > > Cc: Vlastimil Babka <vbabka@suse.cz> > > Cc: Michal Hocko <mhocko@suse.com> > > Signed-off-by: Miles Chen <miles.chen@mediatek.com> > > Fixes: 7e2f2a0cd17c ("mm, page_owner: record page owner for each subpage") > > Thanks. Kirill spotted it earlier and there's a fix pending: > https://lore.kernel.org/linux-mm/20190930122916.14969-2-vbabka@suse.cz/ Great. thanks for the information. Miles > > > --- > > mm/page_owner.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/mm/page_owner.c b/mm/page_owner.c > > index dee931184788..110c3e1987f2 100644 > > --- a/mm/page_owner.c > > +++ b/mm/page_owner.c > > @@ -178,6 +178,7 @@ static inline void __set_page_owner_handle(struct page *page, > > int i; > > > > for (i = 0; i < (1 << order); i++) { > > + page_ext = lookup_page_ext(page + i); > > page_owner = get_page_owner(page_ext); > > page_owner->handle = handle; > > page_owner->order = order; > > @@ -185,8 +186,6 @@ static inline void __set_page_owner_handle(struct page *page, > > page_owner->last_migrate_reason = -1; > > __set_bit(PAGE_EXT_OWNER, &page_ext->flags); > > __set_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags); > > - > > - page_ext = lookup_page_ext(page + i); > > } > > } > > > > >
diff --git a/mm/page_owner.c b/mm/page_owner.c index dee931184788..110c3e1987f2 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -178,6 +178,7 @@ static inline void __set_page_owner_handle(struct page *page, int i; for (i = 0; i < (1 << order); i++) { + page_ext = lookup_page_ext(page + i); page_owner = get_page_owner(page_ext); page_owner->handle = handle; page_owner->order = order; @@ -185,8 +186,6 @@ static inline void __set_page_owner_handle(struct page *page, page_owner->last_migrate_reason = -1; __set_bit(PAGE_EXT_OWNER, &page_ext->flags); __set_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags); - - page_ext = lookup_page_ext(page + i); } }
In __set_page_owner_handle(), we should loop over page [0...(1 << order) - 1] and setup their page_owner structures. Currently, __set_page_owner_handle() update page_ext at the end of the loop, sets the page_owner of (page + 0) twice and misses the page_owner of (page + (1 << order) - 1). Fix it by updating the page_ext at the start of the loop. In i == 0 case: for (i = 0; i < (1 << order); i++) { page_owner = get_page_owner(page_ext); <- page_ext belongs to page + 0 ... page_ext = lookup_page_ext(page + i); <- lookup_page_ext(page + 0) } Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Miles Chen <miles.chen@mediatek.com> Fixes: 7e2f2a0cd17c ("mm, page_owner: record page owner for each subpage") --- mm/page_owner.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)