Commit 963f0cf6 authored by Artem Bityutskiy's avatar Artem Bityutskiy
Browse files

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: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: default avatarAdrian Hunter <Adrian.Hunter@nokia.com>
parent fcabb347

fs/ubifs/sb.c

+29 −6
Original line number Diff line number Diff line
@@ -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);

fs/ubifs/super.c

+12 −2
Original line number Diff line number Diff line
@@ -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;

fs/ubifs/ubifs-media.h

+27 −3
Original line number Diff line number Diff line
@@ -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));



/**

fs/ubifs/ubifs.h

+4 −0
Original line number Diff line number Diff line
@@ -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;

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