state: keep backward compatibility

Previous 'state' variable set variants do not know and use metadata. The
'direct' storage backend's read function honors this, but not its
counterpart the write function. This makes an update of the 'state'
variable set impossible.
This change makes backward compatibility explicit, else it complains in
the read function as well. With some more debug output it helps the
developer to do things right.

Signed-off-by: Juergen Borleis <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 19 insertions, 9 deletions

diff --git a/common/state/backend_bucket_direct.c b/common/state/backend_bucket_direct.c
index 4465ed0e41..958696ed94 100644
--- a/common/state/backend_bucket_direct.c
+++ b/common/state/backend_bucket_direct.c
@@ -69,6 +69,11 @@ static int state_backend_bucket_direct_read(struct state_backend_storage_bucket
 	if (meta.magic == direct_magic) {
 		read_len = meta.written_length;
 	} else {
+		if (!IS_ENABLED(CONFIG_STATE_BACKWARD_COMPATIBLE)) {
+			dev_err(direct->dev, "No meta data header found\n");
+			dev_dbg(direct->dev, "Enable backward compatibility or increase stride size\n");
+			return -EINVAL;
+		}
 		read_len = direct->max_size;
 		ret = lseek(direct->fd, direct->offset, SEEK_SET);
 		if (ret < 0) {
@@ -103,21 +108,26 @@ static int state_backend_bucket_direct_write(struct state_backend_storage_bucket
 	int ret;
 	struct state_backend_storage_bucket_direct_meta meta;
 
-	if (len > direct->max_size - sizeof(meta))
-		return -E2BIG;
-
 	ret = lseek(direct->fd, direct->offset, SEEK_SET);
 	if (ret < 0) {
 		dev_err(direct->dev, "Failed to seek file, %d\n", ret);
 		return ret;
 	}
 
-	meta.magic = direct_magic;
-	meta.written_length = len;
-	ret = write_full(direct->fd, &meta, sizeof(meta));
-	if (ret < 0) {
-		dev_err(direct->dev, "Failed to write metadata to file, %d\n", ret);
-		return ret;
+	/* write the meta data only if there is head room */
+	if (len <= direct->max_size - sizeof(meta)) {
+		meta.magic = direct_magic;
+		meta.written_length = len;
+		ret = write_full(direct->fd, &meta, sizeof(meta));
+		if (ret < 0) {
+			dev_err(direct->dev, "Failed to write metadata to file, %d\n", ret);
+			return ret;
+		}
+	} else {
+		if (!IS_ENABLED(CONFIG_STATE_BACKWARD_COMPATIBLE)) {
+			dev_dbg(direct->dev, "Too small stride size: must skip metadata! Increase stride size\n");
+			return -EINVAL;
+		}
 	}
 
 	ret = write_full(direct->fd, buf, len);