libsqfs: add a threshold for extended directory inodes with index

mksquashfs generates extended inodes if a directory contains 256
entries. libsquashfs so far only generated extended inodes if there
is no other way to encode it. Mimic the behaviour of mksquashfs by
adding a threshold.

For this to work, the "sqfs_inode_set_xattr_index" function has to
be changed to not immediately try to demote inodes to basic types.
The fstree serialization is modified to do that itself if the index
is 0xFFFFFFFF and the target is not a directory inode.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/sqfs/dir_writer.c b/lib/sqfs/dir_writer.c
index a02faa7..ce63a1e 100644
--- a/lib/sqfs/dir_writer.c
+++ b/lib/sqfs/dir_writer.c
@@ -21,6 +21,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+#define DIR_INDEX_THRESHOLD (256)
+
 typedef struct dir_entry_t {
 	struct dir_entry_t *next;
 	sqfs_u64 inode_ref;
@@ -385,6 +387,9 @@ sqfs_inode_generic_t
 		inode->base.type = SQFS_INODE_DIR;
 	}
 
+	if (writer->ent_count >= DIR_INDEX_THRESHOLD)
+		inode->base.type = SQFS_INODE_EXT_DIR;
+
 	if (inode->base.type == SQFS_INODE_DIR) {
 		inode->data.dir.start_block = start_block;
 		inode->data.dir.nlink = writer->ent_count + hlinks + 2;