block/raw-posix: refactor handle_aiocb_write_zeroes a bit

move code dealing with a block device to a separate function. This will
allow to implement additional processing for ordinary files.

Please note, that xfs_code has been moved before checking for
s->has_write_zeroes as xfs_write_zeroes does not touch this flag inside.
This makes code a bit more consistent.

CC: Kevin Wolf <kwolf@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Peter Lieven <pl@kamp.de>
CC: Fam Zheng <famz@redhat.com>
Signed-off-by: NDenis V. Lunev <den@openvz.org>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/raw-posix.c

@@ -914,16 +914,15 @@ static int do_fallocate(int fd, int mode, off_t offset, off_t len)
 }
 #endif
 
-static ssize_t handle_aiocb_write_zeroes(RawPosixAIOData *aiocb)
+static ssize_t handle_aiocb_write_zeroes_block(RawPosixAIOData *aiocb)
 {
-    int ret = -EOPNOTSUPP;
+    int ret = -ENOTSUP;
     BDRVRawState *s = aiocb->bs->opaque;
 
-    if (s->has_write_zeroes == 0) {
+    if (!s->has_write_zeroes) {
         return -ENOTSUP;
     }
 
-    if (aiocb->aio_type & QEMU_AIO_BLKDEV) {
 #ifdef BLKZEROOUT
     do {
         uint64_t range[2] = { aiocb->aio_offset, aiocb->aio_nbytes };
@@ -932,21 +931,30 @@ static ssize_t handle_aiocb_write_zeroes(RawPosixAIOData *aiocb)
         }
     } while (errno == EINTR);
 
-        ret = -errno;
+    ret = translate_err(-errno);
 #endif
-    } else {
+
+    if (ret == -ENOTSUP) {
+        s->has_write_zeroes = false;
+    }
+    return ret;
+}
+
+static ssize_t handle_aiocb_write_zeroes(RawPosixAIOData *aiocb)
+{
+    BDRVRawState *s = aiocb->bs->opaque;
+
+    if (aiocb->aio_type & QEMU_AIO_BLKDEV) {
+        return handle_aiocb_write_zeroes_block(aiocb);
+    }
+
 #ifdef CONFIG_XFS
     if (s->is_xfs) {
         return xfs_write_zeroes(s, aiocb->aio_offset, aiocb->aio_nbytes);
     }
 #endif
-    }
 
-    ret = translate_err(ret);
-    if (ret == -ENOTSUP) {
-        s->has_write_zeroes = false;
-    }
-    return ret;
+    return -ENOTSUP;
 }
 
 static ssize_t handle_aiocb_discard(RawPosixAIOData *aiocb)