[patch 057/128] mm/gup.c: further document vma_permits_fault()

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From: Miles Chen <miles.chen@xxxxxxxxxxxx>
Subject: 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 <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/gup.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/gup.c~mm-gupc-further-document-vma_permits_fault
+++ a/mm/gup.c
@@ -1176,7 +1176,8 @@ static bool vma_permits_fault(struct vm_
  * @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()
_




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