r23977: Im prove the pwrite-patch to tdb_expand_file of r23972:

* prevent infinite loops due to 0 bytes written:
  try once more. if we still get 0 as return,
  set errno to ENOSPC and return -1 (error)

* replace int by correct types (ssize_t and size_t).

* print a warning log message in case "written < requested to write"
  usually this means, that the next call to pwrite will fail
  with return value -1 and set errno accordingly.

  Note that the former error condition "written != requested to write"
  is not a correct error condition of write/pwrite. If this is due
  to an error, a subsequent call to (p)write will reveal the cause
  (typically "no space left on device" - ENOSPC).

Michael
(This used to be commit 7f415d12239fc67eb2c7894c6359b9507fe122c6)

1 files changed, 20 insertions, 7 deletions

diff --git a/source4/lib/tdb/common/io.c b/source4/lib/tdb/common/io.c
index ea925f3895..a24b5e24a2 100644
--- a/source4/lib/tdb/common/io.c
+++ b/source4/lib/tdb/common/io.c
@@ -232,15 +232,28 @@ static int tdb_expand_file(struct tdb_context *tdb, tdb_off_t size, tdb_off_t ad
 	   disk. This must be done with write, not via mmap */
 	memset(buf, TDB_PAD_BYTE, sizeof(buf));
 	while (addition) {
-		int n = addition>sizeof(buf)?sizeof(buf):addition;
-		int ret = pwrite(tdb->fd, buf, n, size);
-		if (ret == -1) {
-			TDB_LOG((tdb, TDB_DEBUG_FATAL, "expand_file write of %d failed (%s)\n", 
-				   n, strerror(errno)));
+		size_t n = addition>sizeof(buf)?sizeof(buf):addition;
+		ssize_t written = pwrite(tdb->fd, buf, n, size);
+		if (written == 0) {
+			/* prevent infinite loops: try _once_ more */
+			written = pwrite(tdb->fd, buf, n, size);
+		}
+		if (written == 0) {
+			/* give up, trying to provide a useful errno */
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "expand_file write "
+				"returned 0 twice: giving up!\n"));
+			errno = ENOSPC;
+			return -1;
+		} else if (written == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "expand_file write of "
+				"%d bytes failed (%s)\n", n, strerror(errno)));
 			return -1;
+		} else if (written != n) {
+			TDB_LOG((tdb, TDB_DEBUG_WARNING, "expand_file: wrote "
+				"only %d of %d bytes - retrying\n", written,n));
 		}
-		addition -= ret;
-		size += ret;
+		addition -= written;
+		size += written;
 	}
 	return 0;
 }