mm/gup.c: further document vma_permits_fault()

Describe the caller's responsibilities when passing FAULT_FLAG_ALLOW_RETRY. Link: http://lkml.kernel.org/r/1586915606.5647.5.camel@mtkswgap22 Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
amitbern-aws · Jun 2, 2020 · 548b6a1 · 548b6a1
1 parent e792031
commit 548b6a1
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/mm/gup.c b/mm/gup.c
@@ -1176,7 +1176,8 @@ static bool vma_permits_fault(struct vm_area_struct *vma,
  * @address:	user address
  * @fault_flags:flags to pass down to handle_mm_fault()
  * @unlocked:	did we unlock the mmap_sem while retrying, maybe NULL if caller
- *		does not allow retry
+ *		does not allow retry. If NULL, the caller must guarantee
+ *		that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY.
  *
  * This is meant to be called in the specific scenario where for locking reasons
  * we try to access user memory in atomic context (within a pagefault_disable()