[PATCH v3] erofs-utils: lib: relax erofs_write_device_table() device table check

[Jonathan Calmels]

Avoid returning an error in erofs_write_device_table()
if a new device slot table hasn't been allocated.
Rationale is to allow erofs_importer_flush_all() to succeed when
dealing with images with pre-existing device slots.

This effectively allows the following:

mkfs.erofs -Enoinline_data a.erofs a/
mkfs.erofs -Enoinline_data b.erofs b/
mkfs.erofs merged.erofs a.erofs b.erofs
mkfs.erofs --incremental=data merged.erofs c/

Signed-off-by: Jonathan Calmels <jcalmels at nvidia.com>
---
 lib/super.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/super.c b/lib/super.c
index a203f96..4a0bb3c 100644
--- a/lib/super.c
+++ b/lib/super.c
@@ -391,8 +391,11 @@ int erofs_write_device_table(struct erofs_sb_info *sbi)
 
 	if (!sbi->extra_devices)
 		goto out;
-	if (!bh)
+	if (!bh) {
+		if (erofs_sb_has_device_table(sbi))
+			return 0;
 		return -EINVAL;
+	}
 
 	pos = erofs_btell(bh, false);
 	if (pos == EROFS_NULL_ADDR) {
-- 
2.53.0