[PATCH 23/28] xor: add a better public API

[Christoph Hellwig]

xor_blocks is very annoying to use, because it is limited to 4 + 1
sources / destinations, has an odd argument order and is completely
undocumented.

Lift the code that loops around it from btrfs and async_tx/async_xor into
common code under the name xor_gen and properly document it.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 lib/raid/xor/xor-core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/raid/xor/xor-core.c b/lib/raid/xor/xor-core.c
index 07e06db32731..2e46b6b83b0a 100644
--- a/lib/raid/xor/xor-core.c
+++ b/lib/raid/xor/xor-core.c
@@ -65,6 +65,8 @@ void xor_gen(void *dest, void **srcs, unsigned int src_cnt, unsigned int bytes)
 {
 	unsigned int src_off = 0;
 
+	WARN_ON_ONCE(in_interrupt());
+	WARN_ON_ONCE(bytes == 0);
 	WARN_ON_ONCE(bytes & 511);
 
 	while (src_cnt > 0) {
-- 
2.47.3