lib/zlib: fix DFLTCC not flushing EOBS when creating raw streams

This commit is based on:
  zlib-ng/zlib-ng@ca99a88

Link: https://lkml.kernel.org/r/20230126131428.1222214-4-zaslonko@linux.ibm.com
Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: mzaslonk

lib/zlib_deflate/deflate.c

@@ -451,17 +451,24 @@ int zlib_deflate(
     Assert(strm->avail_out > 0, "bug2");
 
     if (flush != Z_FINISH) return Z_OK;
-    if (s->noheader) return Z_STREAM_END;
 
-    /* Write the zlib trailer (adler32) */
-    putShortMSB(s, (uInt)(strm->adler >> 16));
-    putShortMSB(s, (uInt)(strm->adler & 0xffff));
+    if (!s->noheader) {
+	/* Write zlib trailer (adler32) */
+	putShortMSB(s, (uInt)(strm->adler >> 16));
+	putShortMSB(s, (uInt)(strm->adler & 0xffff));
+    }
     flush_pending(strm);
     /* If avail_out is zero, the application will call deflate again
      * to flush the rest.
      */
-    s->noheader = -1; /* write the trailer only once! */
-    return s->pending != 0 ? Z_OK : Z_STREAM_END;
+    if (!s->noheader) {
+	s->noheader = -1; /* write the trailer only once! */
+    }
+    if (s->pending == 0) {
+	Assert(s->bi_valid == 0, "bi_buf not flushed");
+	return Z_STREAM_END;
+    }
+    return Z_OK;
 }
 
 /* ========================================================================= */