new helper: iter_is_iovec()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/uio.h

@@ -101,6 +101,11 @@ static inline size_t iov_iter_count(struct iov_iter *i)
 	return i->count;
 }
 
+static inline bool iter_is_iovec(struct iov_iter *i)
+{
+	return !(i->type & (ITER_BVEC | ITER_KVEC));
+}
+
 /*
  * Cap the iov_iter by given limit; note that the second argument is
  * *not* the new size - it's upper limit for such.  Passing it a value

mm/filemap.c

@@ -2464,7 +2464,7 @@ ssize_t generic_perform_write(struct file *file,
 	/*
 	 * Copies from kernel address space cannot fail (NFSD is a big user).
 	 */
-	if (segment_eq(get_fs(), KERNEL_DS))
+	if (!iter_is_iovec(i))
 		flags |= AOP_FLAG_UNINTERRUPTIBLE;
 
 	do {

mm/shmem.c

@@ -1536,7 +1536,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	 * holes of a sparse file, we actually need to allocate those pages,
 	 * and even mark them dirty, so it cannot exceed the max_blocks limit.
 	 */
-	if (segment_eq(get_fs(), KERNEL_DS))
+	if (!iter_is_iovec(to))
 		sgp = SGP_DIRTY;
 
 	index = *ppos >> PAGE_CACHE_SHIFT;