diff options
| -rw-r--r-- | fs/ubifs/replay.c | 75 |
1 files changed, 71 insertions, 4 deletions
diff --git a/fs/ubifs/replay.c b/fs/ubifs/replay.c index 0f50fbfe630..6617280d167 100644 --- a/fs/ubifs/replay.c +++ b/fs/ubifs/replay.c @@ -473,6 +473,65 @@ int ubifs_validate_entry(struct ubifs_info *c, } /** + * is_last_bud - check if the bud is the last in the journal head. + * @c: UBIFS file-system description object + * @bud: bud description object + * + * This function checks if bud @bud is the last bud in its journal head. This + * information is then used by 'replay_bud()' to decide whether the bud can + * have corruptions or not. Indeed, only last buds can be corrupted by power + * cuts. Returns %1 if this is the last bud, and %0 if not. + */ +static int is_last_bud(struct ubifs_info *c, struct ubifs_bud *bud) +{ + struct ubifs_jhead *jh = &c->jheads[bud->jhead]; + struct ubifs_bud *next; + uint32_t data; + int err; + + if (list_is_last(&bud->list, &jh->buds_list)) + return 1; + + /* + * The following is a quirk to make sure we work correctly with UBIFS + * images used with older UBIFS. + * + * Normally, the last bud will be the last in the journal head's list + * of bud. However, there is one exception if the UBIFS image belongs + * to older UBIFS. This is fairly unlikely: one would need to use old + * UBIFS, then have a power cut exactly at the right point, and then + * try to mount this image with new UBIFS. + * + * The exception is: it is possible to have 2 buds A and B, A goes + * before B, and B is the last, bud B is contains no data, and bud A is + * corrupted at the end. The reason is that in older versions when the + * journal code switched the next bud (from A to B), it first added a + * log reference node for the new bud (B), and only after this it + * synchronized the write-buffer of current bud (A). But later this was + * changed and UBIFS started to always synchronize the write-buffer of + * the bud (A) before writing the log reference for the new bud (B). + * + * But because older UBIFS always synchronized A's write-buffer before + * writing to B, we can recognize this exceptional situation but + * checking the contents of bud B - if it is empty, then A can be + * treated as the last and we can recover it. + * + * TODO: remove this piece of code in a couple of years (today it is + * 16.05.2011). + */ + next = list_entry(bud->list.next, struct ubifs_bud, list); + if (!list_is_last(&next->list, &jh->buds_list)) + return 0; + + err = ubi_read(c->ubi, next->lnum, (char *)&data, + next->start, 4); + if (err) + return 0; + + return data == 0xFFFFFFFF; +} + +/** * replay_bud - replay a bud logical eraseblock. * @c: UBIFS file-system description object * @b: bud entry which describes the bud @@ -483,15 +542,23 @@ int ubifs_validate_entry(struct ubifs_info *c, */ static int replay_bud(struct ubifs_info *c, struct bud_entry *b) { + int is_last = is_last_bud(c, b->bud); int err = 0, used = 0, lnum = b->bud->lnum, offs = b->bud->start; - int jhead = b->bud->jhead; struct ubifs_scan_leb *sleb; struct ubifs_scan_node *snod; - dbg_mnt("replay bud LEB %d, head %d, offs %d", lnum, jhead, offs); + dbg_mnt("replay bud LEB %d, head %d, offs %d, is_last %d", + lnum, b->bud->jhead, offs, is_last); - if (c->need_recovery) - sleb = ubifs_recover_leb(c, lnum, offs, c->sbuf, jhead != GCHD); + if (c->need_recovery && is_last) + /* + * Recover only last LEBs in the journal heads, because power + * cuts may cause corruptions only in these LEBs, because only + * these LEBs could possibly be written to at the power cut + * time. + */ + sleb = ubifs_recover_leb(c, lnum, offs, c->sbuf, + b->bud->jhead != GCHD); else sleb = ubifs_scan(c, lnum, offs, c->sbuf, 0); if (IS_ERR(sleb)) |