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-rw-r--r--doc/format.txt9
-rw-r--r--include/sqfs/dir_writer.h7
-rw-r--r--include/sqfs/inode.h11
-rw-r--r--lib/sqfs/dir_writer.c6
4 files changed, 27 insertions, 6 deletions
diff --git a/doc/format.txt b/doc/format.txt
index 41cba78..85a66dc 100644
--- a/doc/format.txt
+++ b/doc/format.txt
@@ -664,6 +664,11 @@
+------+--------------+------------------------------------------------------+
| u16 | file size | Total (uncompressed) size in bytes of the entry |
| | | listing in the directory table, including headers. |
+ | | | |
+ | | | This value is 3 bytes larger than the real listing. |
+ | | | The Linux kernel creates "." and ".." entries for |
+ | | | offsets 0 and 1, and only after 3 looks into the |
+ | | | listing, subtracting 3 from the size. |
+------+--------------+------------------------------------------------------+
| u16 | block offset | The (uncompressed) offset within the metadata block |
| | | in the directory table where the directory listing |
@@ -679,8 +684,8 @@
directory. I.e. a directory with N entries has at least N + 2 link count.
- If the "file size" is set to 0, the directory is empty and there is no
- corresponding listing in the directory table.
+ If the "file size" is set to a value < 4, the directory is empty and there is
+ no corresponding listing in the directory table.
An extended directory can have a listing that is at most 4GiB in size, may
diff --git a/include/sqfs/dir_writer.h b/include/sqfs/dir_writer.h
index 9615a41..7b35fe0 100644
--- a/include/sqfs/dir_writer.h
+++ b/include/sqfs/dir_writer.h
@@ -161,6 +161,11 @@ SQFS_API int sqfs_dir_writer_end(sqfs_dir_writer_t *writer);
* size of the directory listing that is required for the directory inodes.
* And also to determine which kind of directory inode to create.
*
+ * Note that this size is only what was written to disk. SquashFS directory
+ * inodes need you to add 3 to this value, to account for "." and ".." entries
+ * which are not actually stored on disk. The @ref sqfs_dir_writer_create_inode
+ * function takes this into account and adds the 3 internally.
+ *
* @param writer A pointer to a directory writer object.
*
* @return The size of the entire, uncompressed listing in bytes.
@@ -226,6 +231,8 @@ SQFS_API size_t sqfs_dir_writer_get_index_size(const sqfs_dir_writer_t *writer);
* convenience function called @ref sqfs_dir_writer_write_index to write the
* index meta data after writing the inode itself.
*
+ * @note The size is already adjusted for the required off-by-3 value.
+ *
* @param writer A pointer to a directory writer object.
* @param hlinks The number of hard links pointing to the directory.
* @param xattr If set to something other than 0xFFFFFFFF, an extended
diff --git a/include/sqfs/inode.h b/include/sqfs/inode.h
index 0bc33db..8df7158 100644
--- a/include/sqfs/inode.h
+++ b/include/sqfs/inode.h
@@ -400,6 +400,15 @@ struct sqfs_inode_dir_t {
/**
* @brief Combined size of all directory entries and headers in bytes.
+ *
+ * The value stored here is off by 3 bytes, i.e. 3 bytes larger than
+ * the actual listing on disk. The Linux implementation of SquashFS
+ * uses readdir() offsets 0 and 1 to synthesize "." and ".." entries,
+ * and after that looks into the actual directory.
+ *
+ * Why store an off-by-3 value on disk instead of faking it in the
+ * kernel and have something consistent here? Beats me, but that's
+ * how it is implemented.
*/
sqfs_u16 size;
@@ -428,7 +437,7 @@ struct sqfs_inode_dir_ext_t {
sqfs_u32 nlink;
/**
- * @brief Combined size of all directory entries and headers in bytes.
+ * @brief Size of all directory entries and headers in bytes plus 3.
*/
sqfs_u32 size;
diff --git a/lib/sqfs/dir_writer.c b/lib/sqfs/dir_writer.c
index 908bb01..ad44458 100644
--- a/lib/sqfs/dir_writer.c
+++ b/lib/sqfs/dir_writer.c
@@ -379,7 +379,7 @@ sqfs_inode_generic_t
block_offset = writer->dir_ref & 0xFFFF;
if (xattr != 0xFFFFFFFF || start_block > 0xFFFFFFFFUL ||
- writer->dir_size > 0xFFFF) {
+ writer->dir_size > (0xFFFF - 3)) {
inode->base.type = SQFS_INODE_EXT_DIR;
} else {
inode->base.type = SQFS_INODE_DIR;
@@ -388,12 +388,12 @@ sqfs_inode_generic_t
if (inode->base.type == SQFS_INODE_DIR) {
inode->data.dir.start_block = start_block;
inode->data.dir.nlink = writer->ent_count + hlinks + 2;
- inode->data.dir.size = writer->dir_size;
+ inode->data.dir.size = writer->dir_size + 3;
inode->data.dir.offset = block_offset;
inode->data.dir.parent_inode = parent_ino;
} else {
inode->data.dir_ext.nlink = writer->ent_count + hlinks + 2;
- inode->data.dir_ext.size = writer->dir_size;
+ inode->data.dir_ext.size = writer->dir_size + 3;
inode->data.dir_ext.start_block = start_block;
inode->data.dir_ext.parent_inode = parent_ino;
inode->data.dir_ext.offset = block_offset;