return 0;
}
+/**
+ * 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
- * @lnum: bud logical eraseblock number to replay
- * @offs: bud start offset
- * @jhead: journal head to which this bud belongs
- * @free: amount of free space in the bud is returned here
- * @dirty: amount of dirty space from padding and deletion nodes is returned
- * here
+ * @b: bud entry which describes the bud
*
- * This function returns zero in case of success and a negative error code in
- * case of failure.
+ * This function replays bud @bud, recovers it if needed, and adds all nodes
+ * from this bud to the replay list. Returns zero in case of success and a
+ * negative error code in case of failure.
*/
-static int replay_bud(struct ubifs_info *c, int lnum, int offs, int jhead,
- int *free, int *dirty)
+static int replay_bud(struct ubifs_info *c, struct bud_entry *b)
{
- int err = 0, used = 0;
+ int is_last = is_last_bud(c, b->bud);
+ int err = 0, used = 0, lnum = b->bud->lnum, offs = b->bud->start;
struct ubifs_scan_leb *sleb;
struct ubifs_scan_node *snod;
- struct ubifs_bud *bud;
- dbg_mnt("replay bud LEB %d, head %d, offs %d", lnum, jhead, offs);
- if (c->need_recovery)
- sleb = ubifs_recover_leb(c, lnum, offs, c->sbuf, jhead != GCHD);
+ dbg_mnt("replay bud LEB %d, head %d, offs %d, is_last %d",
+ lnum, b->bud->jhead, offs, is_last);
+
+ 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))
goto out;
}
- bud = ubifs_search_bud(c, lnum);
- if (!bud)
- BUG();
-
+ ubifs_assert(ubifs_search_bud(c, lnum));
ubifs_assert(sleb->endpt - offs >= used);
ubifs_assert(sleb->endpt % c->min_io_size == 0);
- *dirty = sleb->endpt - offs - used;
- *free = c->leb_size - sleb->endpt;
- dbg_mnt("bud LEB %d replied: dirty %d, free %d", lnum, *dirty, *free);
+ b->dirty = sleb->endpt - offs - used;
+ b->free = c->leb_size - sleb->endpt;
+ dbg_mnt("bud LEB %d replied: dirty %d, free %d", lnum, b->dirty, b->free);
out:
ubifs_scan_destroy(sleb);
unsigned long long prev_sqnum = 0;
list_for_each_entry(b, &c->replay_buds, list) {
- err = replay_bud(c, b->bud->lnum, b->bud->start, b->bud->jhead,
- &b->free, &b->dirty);
+ err = replay_bud(c, b);
if (err)
return err;
git.openpandora.org / pandora-kernel.git / blobdiff