[PATCH v2] iov_iter: Fix build error without CONFIG_CRYPTO

[Yue Haibing]

From: YueHaibing <yuehaibing@xxxxxxxxxx>

If CONFIG_CRYPTO is not set or set to m,
gcc building warn this:

lib/iov_iter.o: In function `hash_and_copy_to_iter':
iov_iter.c:(.text+0x9129): undefined reference to `crypto_stats_get'
iov_iter.c:(.text+0x9152): undefined reference to `crypto_stats_ahash_update'

Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Fixes: d05f443554b3 ("iov_iter: introduce hash_and_copy_to_iter helper")
Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
---
v2: rework the fix as Al Viro suggested
---
 lib/iov_iter.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 50e77ec..f74fa83 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1531,6 +1531,7 @@ EXPORT_SYMBOL(csum_and_copy_to_iter);
 size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
 		struct iov_iter *i)
 {
+#ifdef CONFIG_CRYPTO
 	struct ahash_request *hash = hashp;
 	struct scatterlist sg;
 	size_t copied;
@@ -1540,6 +1541,9 @@ size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
 	ahash_request_set_crypt(hash, &sg, NULL, copied);
 	crypto_ahash_update(hash);
 	return copied;
+#else
+	return 0;
+#endif
 }
 EXPORT_SYMBOL(hash_and_copy_to_iter);
 
-- 
2.7.4