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() _
