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| author | Artem Bityutskiy <Artem.Bityutskiy@nokia.com> | 2009-03-26 12:51:21 +0200 |
|---|---|---|
| committer | Artem Bityutskiy <Artem.Bityutskiy@nokia.com> | 2009-03-26 16:36:20 +0200 |
| commit | 963f0cf6d116d83c558a8efe9045c1c5ad7aed34 (patch) | |
| tree | 43937f0d742bfac7dfc1a00bae8f72e98dc87425 /fs/ubifs/sb.c | |
| parent | fcabb3479e2b15abfd2d2ef5363295f16e98b2d7 (diff) | |
| download | linux-963f0cf6d116d83c558a8efe9045c1c5ad7aed34.tar.gz linux-963f0cf6d116d83c558a8efe9045c1c5ad7aed34.tar.bz2 linux-963f0cf6d116d83c558a8efe9045c1c5ad7aed34.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>
Diffstat (limited to 'fs/ubifs/sb.c')
| -rw-r--r-- | fs/ubifs/sb.c | 35 |
1 files changed, 29 insertions, 6 deletions
diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c index 0dec47c87c6d..57085e43320f 100644 --- a/fs/ubifs/sb.c +++ b/fs/ubifs/sb.c @@ -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); @@ -532,17 +533,39 @@ 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); - err = -EINVAL; - goto out; + 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) { |