MADV_SPLIT enables HugeTLB HGM which allows for UFFDIO_CONTINUE in
PAGE_SIZE chunks. If a huge-page-aligned address were to be provided,
userspace would be completely unable to take advantage of HGM. That
would then require userspace to know to provide
UFFD_FEATURE_EXACT_ADDRESS.
This patch would make it harder to make a mistake. Instead of requiring
userspace to provide UFFD_FEATURE_EXACT_ADDRESS, always provide a usable
address.
Signed-off-by: James Houghton <jthoughton@xxxxxxxxxx>
---
mm/hugetlb.c | 31 +++++++++++++++----------------
1 file changed, 15 insertions(+), 16 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5af6db52f34e..5b6215e03fe1 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5936,28 +5936,27 @@ static inline vm_fault_t hugetlb_handle_userfault(struct vm_area_struct *vma,
unsigned long addr,
unsigned long reason)
{
+ u32 hash;
+ struct vm_fault vmf;
+
/*
* Don't use the hpage-aligned address if the user has explicitly
* enabled HGM.
*/
if (hugetlb_hgm_advised(vma) && reason == VM_UFFD_MINOR)
- haddr = address & PAGE_MASK;
-
- u32 hash;
- struct vm_fault vmf = {
- .vma = vma,
- .address = haddr,
- .real_address = addr,
- .flags = flags,
+ haddr = addr & PAGE_MASK;
- /*
- * Hard to debug if it ends up being
- * used by a callee that assumes
- * something about the other
- * uninitialized fields... same as in
- * memory.c
- */
- };
+ vmf.vma = vma;
+ vmf.address = haddr;
+ vmf.real_address = addr;
+ vmf.flags = flags;
+ /*
+ * Hard to debug if it ends up being
+ * used by a callee that assumes
+ * something about the other
+ * uninitialized fields... same as in
+ * memory.c
+ */
/*
* vma_lock and hugetlb_fault_mutex must be dropped before handling
--
2.39.0.314.g84b9a713c41-goog
