mm/mprotect.c: optimize error detection in do_mprotect_pkey()

Obviously, the error variable detection of the if statement is
for the mprotect callback function, so it is also put into the
scope of calling callbck.

This is a cleanup which makes this site consistent with the rest of this
function's error handling.

Link: https://lkml.kernel.org/r/20210118133310.98375-1-tianjia.zhang@linux.alibaba.comSigned-off-by: NTianjia Zhang <tianjia.zhang@linux.alibaba.com>
Reported-by: Jia Zhang <zhang.jia@linux.alibaba.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/mprotect.c

@@ -617,10 +617,11 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 		if (tmp > end)
 			tmp = end;
 
-		if (vma->vm_ops && vma->vm_ops->mprotect)
+		if (vma->vm_ops && vma->vm_ops->mprotect) {
 			error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags);
-		if (error)
-			goto out;
+			if (error)
+				goto out;
+		}
 
 		error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
 		if (error)