diff options
author | Artem Bityutskiy <Artem.Bityutskiy@nokia.com> | 2009-03-27 10:21:14 +0100 |
---|---|---|
committer | Wolfgang Denk <wd@denx.de> | 2009-04-04 22:44:22 +0200 |
commit | febd7e4174e54579c9aa165c85c519fe5288f9d2 (patch) | |
tree | 77824e8f6861c68b4151824d2e25cfb1216ee784 /fs/ubifs/ubifs-media.h | |
parent | 852dbfdd56f68eb67d138b306a64e4de58dabb91 (diff) | |
download | talos-obmc-uboot-febd7e4174e54579c9aa165c85c519fe5288f9d2.tar.gz talos-obmc-uboot-febd7e4174e54579c9aa165c85c519fe5288f9d2.zip |
UBIFS: add R/O compatibility
Now UBIFS is supported by u-boot. If we ever decide to change the
media format, then people will have to upgrade their u-boots to
mount new format images. However, very often it is possible to
preserve R/O forward-compatibility, even though the write
forward-compatibility is not preserved.
This patch introduces a new super-block field which stores the
R/O compatibility version.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: Adrian Hunter <Adrian.Hunter@nokia.com>
Signed-off-by: Stefan Roese <sr@denx.de>
Diffstat (limited to 'fs/ubifs/ubifs-media.h')
-rw-r--r-- | fs/ubifs/ubifs-media.h | 30 |
1 files changed, 27 insertions, 3 deletions
diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h index b25fc36cf7..3eee07e0c4 100644 --- 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) @@ -53,7 +75,7 @@ /* * If compressed data length is less than %UBIFS_MIN_COMPRESS_DIFF bytes - * shorter than uncompressed data length, UBIFS preferes to leave this data + * 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 @@ -586,6 +608,7 @@ 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; @@ -612,7 +635,8 @@ 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)); /** |