recovery.c

linux 内核源代码

	journal->j_tail = 0;
	return err;
}

static inline unsigned long long read_tag_block(int tag_bytes, journal_block_tag_t *tag)
{
	unsigned long long block = be32_to_cpu(tag->t_blocknr);
	if (tag_bytes > JBD2_TAG_SIZE32)
		block |= (u64)be32_to_cpu(tag->t_blocknr_high) << 32;
	return block;
}

static int do_one_pass(journal_t *journal,
			struct recovery_info *info, enum passtype pass)
{
	unsigned int		first_commit_ID, next_commit_ID;
	unsigned long		next_log_block;
	int			err, success = 0;
	journal_superblock_t *	sb;
	journal_header_t *	tmp;
	struct buffer_head *	bh;
	unsigned int		sequence;
	int			blocktype;
	int			tag_bytes = journal_tag_bytes(journal);

	/* Precompute the maximum metadata descriptors in a descriptor block */
	int			MAX_BLOCKS_PER_DESC;
	MAX_BLOCKS_PER_DESC = ((journal->j_blocksize-sizeof(journal_header_t))
			       / tag_bytes);

	/*
	 * First thing is to establish what we expect to find in the log
	 * (in terms of transaction IDs), and where (in terms of log
	 * block offsets): query the superblock.
	 */

	sb = journal->j_superblock;
	next_commit_ID = be32_to_cpu(sb->s_sequence);
	next_log_block = be32_to_cpu(sb->s_start);

	first_commit_ID = next_commit_ID;
	if (pass == PASS_SCAN)
		info->start_transaction = first_commit_ID;

	jbd_debug(1, "Starting recovery pass %d\n", pass);

	/*
	 * Now we walk through the log, transaction by transaction,
	 * making sure that each transaction has a commit block in the
	 * expected place.  Each complete transaction gets replayed back
	 * into the main filesystem.
	 */

	while (1) {
		int			flags;
		char *			tagp;
		journal_block_tag_t *	tag;
		struct buffer_head *	obh;
		struct buffer_head *	nbh;

		cond_resched();		/* We're under lock_kernel() */

		/* If we already know where to stop the log traversal,
		 * check right now that we haven't gone past the end of
		 * the log. */

		if (pass != PASS_SCAN)
			if (tid_geq(next_commit_ID, info->end_transaction))
				break;

		jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
			  next_commit_ID, next_log_block, journal->j_last);

		/* Skip over each chunk of the transaction looking
		 * either the next descriptor block or the final commit
		 * record. */

		jbd_debug(3, "JBD: checking block %ld\n", next_log_block);
		err = jread(&bh, journal, next_log_block);
		if (err)
			goto failed;

		next_log_block++;
		wrap(journal, next_log_block);

		/* What kind of buffer is it?
		 *
		 * If it is a descriptor block, check that it has the
		 * expected sequence number.  Otherwise, we're all done
		 * here. */

		tmp = (journal_header_t *)bh->b_data;

		if (tmp->h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER)) {
			brelse(bh);
			break;
		}

		blocktype = be32_to_cpu(tmp->h_blocktype);
		sequence = be32_to_cpu(tmp->h_sequence);
		jbd_debug(3, "Found magic %d, sequence %d\n",
			  blocktype, sequence);

		if (sequence != next_commit_ID) {
			brelse(bh);
			break;
		}

		/* OK, we have a valid descriptor block which matches
		 * all of the sequence number checks.  What are we going
		 * to do with it?  That depends on the pass... */

		switch(blocktype) {
		case JBD2_DESCRIPTOR_BLOCK:
			/* If it is a valid descriptor block, replay it
			 * in pass REPLAY; otherwise, just skip over the
			 * blocks it describes. */
			if (pass != PASS_REPLAY) {
				next_log_block += count_tags(journal, bh);
				wrap(journal, next_log_block);
				brelse(bh);
				continue;
			}

			/* A descriptor block: we can now write all of
			 * the data blocks.  Yay, useful work is finally
			 * getting done here! */

			tagp = &bh->b_data[sizeof(journal_header_t)];
			while ((tagp - bh->b_data + tag_bytes)
			       <= journal->j_blocksize) {
				unsigned long io_block;

				tag = (journal_block_tag_t *) tagp;
				flags = be32_to_cpu(tag->t_flags);

				io_block = next_log_block++;
				wrap(journal, next_log_block);
				err = jread(&obh, journal, io_block);
				if (err) {
					/* Recover what we can, but
					 * report failure at the end. */
					success = err;
					printk (KERN_ERR
						"JBD: IO error %d recovering "
						"block %ld in log\n",
						err, io_block);
				} else {
					unsigned long long blocknr;

					J_ASSERT(obh != NULL);
					blocknr = read_tag_block(tag_bytes,
								 tag);

					/* If the block has been
					 * revoked, then we're all done
					 * here. */
					if (jbd2_journal_test_revoke
					    (journal, blocknr,
					     next_commit_ID)) {
						brelse(obh);
						++info->nr_revoke_hits;
						goto skip_write;
					}

					/* Find a buffer for the new
					 * data being restored */
					nbh = __getblk(journal->j_fs_dev,
							blocknr,
							journal->j_blocksize);
					if (nbh == NULL) {
						printk(KERN_ERR
						       "JBD: Out of memory "
						       "during recovery.\n");
						err = -ENOMEM;
						brelse(bh);
						brelse(obh);
						goto failed;
					}

					lock_buffer(nbh);
					memcpy(nbh->b_data, obh->b_data,
							journal->j_blocksize);
					if (flags & JBD2_FLAG_ESCAPE) {
						*((__be32 *)bh->b_data) =
						cpu_to_be32(JBD2_MAGIC_NUMBER);
					}

					BUFFER_TRACE(nbh, "marking dirty");
					set_buffer_uptodate(nbh);
					mark_buffer_dirty(nbh);
					BUFFER_TRACE(nbh, "marking uptodate");
					++info->nr_replays;
					/* ll_rw_block(WRITE, 1, &nbh); */
					unlock_buffer(nbh);
					brelse(obh);
					brelse(nbh);
				}

			skip_write:
				tagp += tag_bytes;
				if (!(flags & JBD2_FLAG_SAME_UUID))
					tagp += 16;

				if (flags & JBD2_FLAG_LAST_TAG)
					break;
			}

			brelse(bh);
			continue;

		case JBD2_COMMIT_BLOCK:
			/* Found an expected commit block: not much to
			 * do other than move on to the next sequence
			 * number. */
			brelse(bh);
			next_commit_ID++;
			continue;

		case JBD2_REVOKE_BLOCK:
			/* If we aren't in the REVOKE pass, then we can
			 * just skip over this block. */
			if (pass != PASS_REVOKE) {
				brelse(bh);
				continue;
			}

			err = scan_revoke_records(journal, bh,
						  next_commit_ID, info);
			brelse(bh);
			if (err)
				goto failed;
			continue;

		default:
			jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
				  blocktype);
			brelse(bh);
			goto done;
		}
	}

 done:
	/*
	 * We broke out of the log scan loop: either we came to the
	 * known end of the log or we found an unexpected block in the
	 * log.  If the latter happened, then we know that the "current"
	 * transaction marks the end of the valid log.
	 */

	if (pass == PASS_SCAN)
		info->end_transaction = next_commit_ID;
	else {
		/* It's really bad news if different passes end up at
		 * different places (but possible due to IO errors). */
		if (info->end_transaction != next_commit_ID) {
			printk (KERN_ERR "JBD: recovery pass %d ended at "
				"transaction %u, expected %u\n",
				pass, next_commit_ID, info->end_transaction);
			if (!success)
				success = -EIO;
		}
	}

	return success;

 failed:
	return err;
}


/* Scan a revoke record, marking all blocks mentioned as revoked. */

static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
			       tid_t sequence, struct recovery_info *info)
{
	jbd2_journal_revoke_header_t *header;
	int offset, max;
	int record_len = 4;

	header = (jbd2_journal_revoke_header_t *) bh->b_data;
	offset = sizeof(jbd2_journal_revoke_header_t);
	max = be32_to_cpu(header->r_count);

	if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
		record_len = 8;

	while (offset + record_len <= max) {
		unsigned long long blocknr;
		int err;

		if (record_len == 4)
			blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
		else
			blocknr = be64_to_cpu(* ((__be64 *) (bh->b_data+offset)));
		offset += record_len;
		err = jbd2_journal_set_revoke(journal, blocknr, sequence);
		if (err)
			return err;
		++info->nr_revokes;
	}
	return 0;
}