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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>
This commit is contained in:
Artem Bityutskiy 2009-03-26 12:51:21 +02:00
parent fcabb3479e
commit 963f0cf6d1
4 changed files with 72 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
fs/ubifs/sb.c
View File

@ -193,6 +193,7 @@ static int create_default_filesystem(struct ubifs_info *c)
if (tmp64 > DEFAULT_MAX_RP_SIZE)
tmp64 = DEFAULT_MAX_RP_SIZE;
sup->rp_size = cpu_to_le64(tmp64);
sup->ro_compat_version = cpu_to_le32(UBIFS_RO_COMPAT_VERSION);
err = ubifs_write_node(c, sup, UBIFS_SB_NODE_SZ, 0, 0, UBI_LONGTERM);
kfree(sup);
@ -532,19 +533,41 @@ int ubifs_read_superblock(struct ubifs_info *c)
if (IS_ERR(sup))
return PTR_ERR(sup);
c->fmt_version = le32_to_cpu(sup->fmt_version);
c->ro_compat_version = le32_to_cpu(sup->ro_compat_version);
/*
* The software supports all previous versions but not future versions,
* due to the unavailability of time-travelling equipment.
*/
c->fmt_version = le32_to_cpu(sup->fmt_version);
if (c->fmt_version > UBIFS_FORMAT_VERSION) {
ubifs_err("on-flash format version is %d, but software only "
"supports up to version %d", c->fmt_version,
UBIFS_FORMAT_VERSION);
struct super_block *sb = c->vfs_sb;
int mounting_ro = sb->s_flags & MS_RDONLY;
ubifs_assert(!c->ro_media || mounting_ro);
if (!mounting_ro ||
c->ro_compat_version > UBIFS_RO_COMPAT_VERSION) {
ubifs_err("on-flash format version is w%d/r%d, but "
"software only supports up to version "
"w%d/r%d", c->fmt_version,
c->ro_compat_version, UBIFS_FORMAT_VERSION,
UBIFS_RO_COMPAT_VERSION);
if (c->ro_compat_version <= UBIFS_RO_COMPAT_VERSION) {
ubifs_msg("only R/O mounting is possible");
err = -EROFS;
} else
err = -EINVAL;
goto out;
}
/*
* The FS is mounted R/O, and the media format is
* R/O-compatible with the UBIFS implementation, so we can
* mount.
*/
c->rw_incompat = 1;
}
if (c->fmt_version < 3) {
ubifs_err("on-flash format version %d is not supported",
c->fmt_version);

14
fs/ubifs/super.c
View File

@ -1351,8 +1351,9 @@ static int mount_ubifs(struct ubifs_info *c)
x = (long long)c->log_lebs * c->leb_size + c->max_bud_bytes;
ubifs_msg("journal size: %lld bytes (%lld KiB, %lld MiB, %d "
"LEBs)", x, x >> 10, x >> 20, c->log_lebs + c->max_bud_cnt);
ubifs_msg("media format: %d (latest is %d)",
c->fmt_version, UBIFS_FORMAT_VERSION);
ubifs_msg("media format: w%d/r%d (latest is w%d/r%d)",
c->fmt_version, c->ro_compat_version,
UBIFS_FORMAT_VERSION, UBIFS_RO_COMPAT_VERSION);
ubifs_msg("default compressor: %s", ubifs_compr_name(c->default_compr));
ubifs_msg("reserved for root: %llu bytes (%llu KiB)",
c->report_rp_size, c->report_rp_size >> 10);
@ -1492,6 +1493,15 @@ static int ubifs_remount_rw(struct ubifs_info *c)
{
int err, lnum;
if (c->rw_incompat) {
ubifs_err("the file-system is not R/W-compatible");
ubifs_msg("on-flash format version is w%d/r%d, but software "
"only supports up to version w%d/r%d", c->fmt_version,
c->ro_compat_version, UBIFS_FORMAT_VERSION,
UBIFS_RO_COMPAT_VERSION);
return -EROFS;
}
mutex_lock(&c->umount_mutex);
dbg_save_space_info(c);
c->remounting_rw = 1;

30
fs/ubifs/ubifs-media.h
View File

@ -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));
/**

4
fs/ubifs/ubifs.h
View File

@ -934,6 +934,7 @@ struct ubifs_debug_info;
* by @commit_sem
* @cnt_lock: protects @highest_inum and @max_sqnum counters
* @fmt_version: UBIFS on-flash format version
* @ro_compat_version: R/O compatibility version
* @uuid: UUID from super block
*
* @lhead_lnum: log head logical eraseblock number
@ -966,6 +967,7 @@ struct ubifs_debug_info;
* recovery)
* @bulk_read: enable bulk-reads
* @default_compr: default compression algorithm (%UBIFS_COMPR_LZO, etc)
* @rw_incompat: the media is not R/W compatible
*
* @tnc_mutex: protects the Tree Node Cache (TNC), @zroot, @cnext, @enext, and
* @calc_idx_sz
@ -1179,6 +1181,7 @@ struct ubifs_info {
unsigned long long cmt_no;
spinlock_t cnt_lock;
int fmt_version;
int ro_compat_version;
unsigned char uuid[16];
int lhead_lnum;
@ -1207,6 +1210,7 @@ struct ubifs_info {
unsigned int no_chk_data_crc:1;
unsigned int bulk_read:1;
unsigned int default_compr:2;
unsigned int rw_incompat:1;
struct mutex tnc_mutex;
struct ubifs_zbranch zroot;