Merge branch 'linus' into cont_syslog

[safe/jmp/linux-2.6] / fs / ubifs / ubifs-media.h

diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h
index bd2121f..191ca78 100644 (file)
--- a/fs/ubifs/ubifs-media.h
+++ b/fs/ubifs/ubifs-media.h
@@ -36,9 +36,31 @@
 /* UBIFS node magic number (must not have the padding byte first or last) */
 #define UBIFS_NODE_MAGIC  0x06101831
 
-/* UBIFS on-flash format version */
+/*
+ * UBIFS on-flash format version. This version is increased when the on-flash
+ * format is changing. If this happens, UBIFS is will support older versions as
+ * well. But older UBIFS code will not support newer formats. Format changes
+ * will be rare and only when absolutely necessary, e.g. to fix a bug or to add
+ * a new feature.
+ *
+ * UBIFS went into mainline kernel with format version 4. The older formats
+ * were development formats.
+ */
 #define UBIFS_FORMAT_VERSION 4
 
+/*
+ * Read-only compatibility version. If the UBIFS format is changed, older UBIFS
+ * implementations will not be able to mount newer formats in read-write mode.
+ * However, depending on the change, it may be possible to mount newer formats
+ * in R/O mode. This is indicated by the R/O compatibility version which is
+ * stored in the super-block.
+ *
+ * This is needed to support boot-loaders which only need R/O mounting. With
+ * this flag it is possible to do UBIFS format changes without a need to update
+ * boot-loaders.
+ */
+#define UBIFS_RO_COMPAT_VERSION 0
+
 /* Minimum logical eraseblock size in bytes */
 #define UBIFS_MIN_LEB_SZ (15*1024)
 
@@ -51,6 +73,13 @@
  */
 #define UBIFS_MIN_COMPR_LEN 128
 
+/*
+ * If compressed data length is less than %UBIFS_MIN_COMPRESS_DIFF bytes
+ * shorter than uncompressed data length, UBIFS prefers to leave this data
+ * node uncompress, because it'll be read faster.
+ */
+#define UBIFS_MIN_COMPRESS_DIFF 64
+
 /* Root inode number */
 #define UBIFS_ROOT_INO 1
 
@@ -75,7 +104,6 @@
  */
 #define UBIFS_BLOCK_SIZE  4096
 #define UBIFS_BLOCK_SHIFT 12
-#define UBIFS_BLOCK_MASK  0x00000FFF
 
 /* UBIFS padding byte pattern (must not be first or last byte of node magic) */
 #define UBIFS_PADDING_BYTE 0xCE
@@ -87,7 +115,7 @@
 #define UBIFS_SK_LEN 8
 
 /* Minimum index tree fanout */
-#define UBIFS_MIN_FANOUT 2
+#define UBIFS_MIN_FANOUT 3
 
 /* Maximum number of levels in UBIFS indexing B-tree */
 #define UBIFS_MAX_LEVELS 512
@@ -107,6 +135,13 @@
 /* The key is always at the same position in all keyed nodes */
 #define UBIFS_KEY_OFFSET offsetof(struct ubifs_ino_node, key)
 
+/* Garbage collector journal head number */
+#define UBIFS_GC_HEAD   0
+/* Base journal head number */
+#define UBIFS_BASE_HEAD 1
+/* Data journal head number */
+#define UBIFS_DATA_HEAD 2
+
 /*
  * LEB Properties Tree node types.
  *
@@ -580,6 +615,7 @@ struct ubifs_pad_node {
  * @padding2: reserved for future, zeroes
  * @time_gran: time granularity in nanoseconds
  * @uuid: UUID generated when the file system image was created
+ * @ro_compat_version: UBIFS R/O compatibility version
  */
 struct ubifs_sb_node {
        struct ubifs_ch ch;
@@ -606,7 +642,8 @@ struct ubifs_sb_node {
        __le64 rp_size;
        __le32 time_gran;
        __u8 uuid[16];
-       __u8 padding2[3972];
+       __le32 ro_compat_version;
+       __u8 padding2[3968];
 } __attribute__ ((packed));
 
 /**