| Message ID | 20210913115021.27597-1-linmiaohe@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] mm/page_isolation: don't putback unisolated page | expand |
On 13.09.21 13:50, Miaohe Lin wrote: > If __isolate_free_page() failed, due to zone watermark check, the page is > still on the free list. But this page will be put back to free list again > via __putback_isolated_page() now. This may trigger page->flags checks in > __free_one_page() if PageReported is set. Or we will corrupt the free list > because list_add() will be called for pages already on another list. > > Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock") > Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> > --- > v1->v2: > Add VM_WARN_ON to catch unexpected isolating failure. > --- > mm/page_isolation.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index f93cc63d8fa1..f67c4c70f17f 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -94,8 +94,13 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) > buddy = page + (buddy_pfn - pfn); > > if (!is_migrate_isolate_page(buddy)) { > - __isolate_free_page(page, order); > - isolated_page = true; > + isolated_page = !!__isolate_free_page(page, order); > + /* > + * Isolating a free page in an isolated pageblock > + * is expected to always work as watermarks don't > + * apply here. > + */ > + VM_WARN_ON(!isolated_page); Didn't we discuss that this can never happen? In that case, the patch description+subject needs updating and the "Fixes" line would be wrong. > } > } > } >
On 2021/9/13 20:15, David Hildenbrand wrote: > On 13.09.21 13:50, Miaohe Lin wrote: >> If __isolate_free_page() failed, due to zone watermark check, the page is >> still on the free list. But this page will be put back to free list again >> via __putback_isolated_page() now. This may trigger page->flags checks in >> __free_one_page() if PageReported is set. Or we will corrupt the free list >> because list_add() will be called for pages already on another list. >> >> Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock") >> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> >> --- >> v1->v2: >> Add VM_WARN_ON to catch unexpected isolating failure. >> --- >> mm/page_isolation.c | 9 +++++++-- >> 1 file changed, 7 insertions(+), 2 deletions(-) >> >> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >> index f93cc63d8fa1..f67c4c70f17f 100644 >> --- a/mm/page_isolation.c >> +++ b/mm/page_isolation.c >> @@ -94,8 +94,13 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) >> buddy = page + (buddy_pfn - pfn); >> if (!is_migrate_isolate_page(buddy)) { >> - __isolate_free_page(page, order); >> - isolated_page = true; >> + isolated_page = !!__isolate_free_page(page, order); >> + /* >> + * Isolating a free page in an isolated pageblock >> + * is expected to always work as watermarks don't >> + * apply here. >> + */ >> + VM_WARN_ON(!isolated_page); > > > Didn't we discuss that this can never happen? > > In that case, the patch description+subject needs updating and the "Fixes" line would be wrong. > I thought this might need a Fixes tag... Will change all of these. Many thanks. >> } >> } >> } >> > >
diff --git a/mm/page_isolation.c b/mm/page_isolation.c index f93cc63d8fa1..f67c4c70f17f 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -94,8 +94,13 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) buddy = page + (buddy_pfn - pfn); if (!is_migrate_isolate_page(buddy)) { - __isolate_free_page(page, order); - isolated_page = true; + isolated_page = !!__isolate_free_page(page, order); + /* + * Isolating a free page in an isolated pageblock + * is expected to always work as watermarks don't + * apply here. + */ + VM_WARN_ON(!isolated_page); } } }
If __isolate_free_page() failed, due to zone watermark check, the page is still on the free list. But this page will be put back to free list again via __putback_isolated_page() now. This may trigger page->flags checks in __free_one_page() if PageReported is set. Or we will corrupt the free list because list_add() will be called for pages already on another list. Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock") Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> --- v1->v2: Add VM_WARN_ON to catch unexpected isolating failure. --- mm/page_isolation.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)