| Message ID | 20220329160440.193848-11-david@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: COW fixes part 2: reliable GUP pins of anonymous pages | expand |
On 3/29/22 18:04, David Hildenbrand wrote: > We can already theoretically fail to unmap (still having page_mapped()) in > case arch_unmap_one() fails, which can happen on sparc. Failures to > unmap are handled gracefully, just as if there are other references on > the target page: freezing the refcount in split_huge_page_to_list() > will fail if still mapped and we'll simply remap. > > In commit 504e070dc08f ("mm: thp: replace DEBUG_VM BUG with VM_WARN when > unmap fails for split") we already converted to VM_WARN_ON_ONCE_PAGE, > let's get rid of it completely now. > > This is a preparation for making try_to_migrate() fail on anonymous pages > with GUP pins, which will make this VM_WARN_ON_ONCE_PAGE trigger more > frequently. > > Reported-by: Yang Shi <shy828301@gmail.com> > Reviewed-by: Yang Shi <shy828301@gmail.com> > Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > mm/huge_memory.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index dd16819c5edc..70298431e128 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2241,8 +2241,6 @@ static void unmap_page(struct page *page) > try_to_migrate(folio, ttu_flags); > else > try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK); > - > - VM_WARN_ON_ONCE_PAGE(page_mapped(page), page); > } > > static void remap_page(struct folio *folio, unsigned long nr)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index dd16819c5edc..70298431e128 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2241,8 +2241,6 @@ static void unmap_page(struct page *page) try_to_migrate(folio, ttu_flags); else try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK); - - VM_WARN_ON_ONCE_PAGE(page_mapped(page), page); } static void remap_page(struct folio *folio, unsigned long nr)
We can already theoretically fail to unmap (still having page_mapped()) in case arch_unmap_one() fails, which can happen on sparc. Failures to unmap are handled gracefully, just as if there are other references on the target page: freezing the refcount in split_huge_page_to_list() will fail if still mapped and we'll simply remap. In commit 504e070dc08f ("mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split") we already converted to VM_WARN_ON_ONCE_PAGE, let's get rid of it completely now. This is a preparation for making try_to_migrate() fail on anonymous pages with GUP pins, which will make this VM_WARN_ON_ONCE_PAGE trigger more frequently. Reported-by: Yang Shi <shy828301@gmail.com> Reviewed-by: Yang Shi <shy828301@gmail.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- mm/huge_memory.c | 2 -- 1 file changed, 2 deletions(-)