erofs-utils: introduce ondisk compression cfgs

Add support to generate ondisk compression cfgs, which can generate
lz4 compression cfgs now.

Link: https://lore.kernel.org/r/20210411034844.12673-3-xiang@kernel.org
Signed-off-by: Gao Xiang <xiang@kernel.org>

3 files changed, 19 insertions, 3 deletions

diff --git a/include/erofs/compress.h b/include/erofs/compress.h
index 952f287..d234e8b 100644
--- a/include/erofs/compress.h
+++ b/include/erofs/compress.h
@@ -18,7 +18,7 @@
 
 int erofs_write_compressed_file(struct erofs_inode *inode);
 
-int z_erofs_compress_init(void);
+int z_erofs_compress_init(struct erofs_buffer_head *bh);
 int z_erofs_compress_exit(void);
 
 const char *z_erofs_list_available_compressors(unsigned int i);
diff --git a/include/erofs/internal.h b/include/erofs/internal.h
index 3849980..6e481fa 100644
--- a/include/erofs/internal.h
+++ b/include/erofs/internal.h
@@ -79,6 +79,8 @@ struct erofs_sb_info {
 	u64 inos;
 
 	u8 uuid[16];
+
+	u16 available_compr_algs;
 	u16 lz4_max_distance;
 };
 
@@ -105,6 +107,7 @@ static inline void erofs_sb_clear_##name(void) \
 }
 
 EROFS_FEATURE_FUNCS(lz4_0padding, incompat, INCOMPAT_LZ4_0PADDING)
+EROFS_FEATURE_FUNCS(compr_cfgs, incompat, INCOMPAT_COMPR_CFGS)
 EROFS_FEATURE_FUNCS(sb_chksum, compat, COMPAT_SB_CHKSUM)
 
 #define EROFS_I_EA_INITED	(1 << 0)
diff --git a/include/erofs_fs.h b/include/erofs_fs.h
index ae2305c..a24deb0 100644
--- a/include/erofs_fs.h
+++ b/include/erofs_fs.h
@@ -20,7 +20,10 @@
  * be incompatible with this kernel version.
  */
 #define EROFS_FEATURE_INCOMPAT_LZ4_0PADDING	0x00000001
-#define EROFS_ALL_FEATURE_INCOMPAT		EROFS_FEATURE_INCOMPAT_LZ4_0PADDING
+#define EROFS_FEATURE_INCOMPAT_COMPR_CFGS	0x00000002
+#define EROFS_ALL_FEATURE_INCOMPAT		\
+	(EROFS_FEATURE_INCOMPAT_LZ4_0PADDING | \
+	 EROFS_FEATURE_INCOMPAT_COMPR_CFGS)
 
 /* 128-byte erofs on-disk super block */
 struct erofs_super_block {
@@ -41,7 +44,11 @@ struct erofs_super_block {
 	__u8 uuid[16];          /* 128-bit uuid for volume */
 	__u8 volume_name[16];   /* volume name */
 	__le32 feature_incompat;
-	__le16 lz4_max_distance;
+	union {
+		/* bitmap for available compression algorithms */
+		__le16 available_compr_algs;
+		__le16 lz4_max_distance;
+	} u1;
 	__u8 reserved2[42];
 };
 
@@ -198,6 +205,12 @@ enum {
 	Z_EROFS_COMPRESSION_MAX
 };
 
+/* 14 bytes (+ length field = 16 bytes) */
+struct z_erofs_lz4_cfgs {
+	__le16 max_distance;
+	u8 reserved[12];
+} __packed;
+
 /*
  * bit 0 : COMPACTED_2B indexes (0 - off; 1 - on)
  *  e.g. for 4k logical cluster size,      4B        if compacted 2B is off;