file-posix: Handle EINTR in preallocation=full write

Cc: qemu-stable@nongnu.org
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit a1c81f4f)
 Conflicts:
	block/file-posix.c
* avoid dep on 93f4e2ff by adding check to raw_regular_truncate instead
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

block/file-posix.c

@@ -1728,6 +1728,9 @@ static int raw_regular_truncate(int fd, int64_t offset, PreallocMode prealloc,
             num = MIN(left, 65536);
             result = write(fd, buf, num);
             if (result < 0) {
+                if (errno == EINTR) {
+                    continue;
+                }
                 result = -errno;
                 error_setg_errno(errp, -result,
                                  "Could not write zeros for preallocation");