[linux.git] / fs / jbd / recovery.c

/*
 * linux/fs/recovery.c
 * 
 * Written by Stephen C. Tweedie <[email protected]>, 1999
 *
 * Copyright 1999-2000 Red Hat Software --- All Rights Reserved
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * Journal recovery routines for the generic filesystem journaling code;
 * part of the ext2fs journaling system.  
 */

#ifndef __KERNEL__
#include "jfs_user.h"
#else
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd.h>
#include <linux/errno.h>
#include <linux/slab.h>
#endif

/*
 * Maintain information about the progress of the recovery job, so that
 * the different passes can carry information between them. 
 */
struct recovery_info 
{
	tid_t		start_transaction;
	tid_t		end_transaction;

	int		nr_replays;
	int		nr_revokes;
	int		nr_revoke_hits;
};

enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
static int do_one_pass(journal_t *journal,
				struct recovery_info *info, enum passtype pass);
static int scan_revoke_records(journal_t *, struct buffer_head *,
				tid_t, struct recovery_info *);

#ifdef __KERNEL__

/* Release readahead buffers after use */
void journal_brelse_array(struct buffer_head *b[], int n)
{
	while (--n >= 0)
		brelse (b[n]);
}


/*
 * When reading from the journal, we are going through the block device
 * layer directly and so there is no readahead being done for us.  We
 * need to implement any readahead ourselves if we want it to happen at
 * all.  Recovery is basically one long sequential read, so make sure we
 * do the IO in reasonably large chunks.
 *
 * This is not so critical that we need to be enormously clever about
 * the readahead size, though.  128K is a purely arbitrary, good-enough
 * fixed value.
 */

#define MAXBUF 8
static int do_readahead(journal_t *journal, unsigned int start)
{
	int err;
	unsigned int max, nbufs, next;
	unsigned long blocknr;
	struct buffer_head *bh;

	struct buffer_head * bufs[MAXBUF];

	/* Do up to 128K of readahead */
	max = start + (128 * 1024 / journal->j_blocksize);
	if (max > journal->j_maxlen)
		max = journal->j_maxlen;

	/* Do the readahead itself.  We'll submit MAXBUF buffer_heads at
	 * a time to the block device IO layer. */

	nbufs = 0;

	for (next = start; next < max; next++) {
		err = journal_bmap(journal, next, &blocknr);

		if (err) {
			printk (KERN_ERR "JBD: bad block at offset %u\n",
				next);
			goto failed;
		}

		bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
		if (!bh) {
			err = -ENOMEM;
			goto failed;
		}

		if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
			bufs[nbufs++] = bh;
			if (nbufs == MAXBUF) {
				ll_rw_block(READ, nbufs, bufs);
				journal_brelse_array(bufs, nbufs);
				nbufs = 0;
			}
		} else
			brelse(bh);
	}

	if (nbufs)
		ll_rw_block(READ, nbufs, bufs);
	err = 0;

failed:
	if (nbufs) 
		journal_brelse_array(bufs, nbufs);
	return err;
}

#endif /* __KERNEL__ */


/*
 * Read a block from the journal
 */

static int jread(struct buffer_head **bhp, journal_t *journal, 
		 unsigned int offset)
{
	int err;
	unsigned long blocknr;
	struct buffer_head *bh;

	*bhp = NULL;

	if (offset >= journal->j_maxlen) {
		printk(KERN_ERR "JBD: corrupted journal superblock\n");
		return -EIO;
	}

	err = journal_bmap(journal, offset, &blocknr);

	if (err) {
		printk (KERN_ERR "JBD: bad block at offset %u\n",
			offset);
		return err;
	}

	bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
	if (!bh)
		return -ENOMEM;

	if (!buffer_uptodate(bh)) {
		/* If this is a brand new buffer, start readahead.
                   Otherwise, we assume we are already reading it.  */
		if (!buffer_req(bh))
			do_readahead(journal, offset);
		wait_on_buffer(bh);
	}

	if (!buffer_uptodate(bh)) {
		printk (KERN_ERR "JBD: Failed to read block at offset %u\n",
			offset);
		brelse(bh);
		return -EIO;
	}

	*bhp = bh;
	return 0;
}


/*
 * Count the number of in-use tags in a journal descriptor block.
 */

static int count_tags(struct buffer_head *bh, int size)
{
	char *			tagp;
	journal_block_tag_t *	tag;
	int			nr = 0;

	tagp = &bh->b_data[sizeof(journal_header_t)];

	while ((tagp - bh->b_data + sizeof(journal_block_tag_t)) <= size) {
		tag = (journal_block_tag_t *) tagp;

		nr++;
		tagp += sizeof(journal_block_tag_t);
		if (!(tag->t_flags & cpu_to_be32(JFS_FLAG_SAME_UUID)))
			tagp += 16;

		if (tag->t_flags & cpu_to_be32(JFS_FLAG_LAST_TAG))
			break;
	}

	return nr;
}


/* Make sure we wrap around the log correctly! */
#define wrap(journal, var)						\
do {									\
	if (var >= (journal)->j_last)					\
		var -= ((journal)->j_last - (journal)->j_first);	\
} while (0)

/**
 * int journal_recover(journal_t *journal) - recovers a on-disk journal
 * @journal: the journal to recover
 * 
 * The primary function for recovering the log contents when mounting a
 * journaled device.  
 *
 * Recovery is done in three passes.  In the first pass, we look for the
 * end of the log.  In the second, we assemble the list of revoke
 * blocks.  In the third and final pass, we replay any un-revoked blocks
 * in the log.  
 */
int journal_recover(journal_t *journal)
{
	int			err;
	journal_superblock_t *	sb;

	struct recovery_info	info;

	memset(&info, 0, sizeof(info));
	sb = journal->j_superblock;

	/* 
	 * The journal superblock's s_start field (the current log head)
	 * is always zero if, and only if, the journal was cleanly
	 * unmounted.  
	 */

	if (!sb->s_start) {
		jbd_debug(1, "No recovery required, last transaction %d\n",
			  be32_to_cpu(sb->s_sequence));
		journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
		return 0;
	}

	err = do_one_pass(journal, &info, PASS_SCAN);
	if (!err)
		err = do_one_pass(journal, &info, PASS_REVOKE);
	if (!err)
		err = do_one_pass(journal, &info, PASS_REPLAY);

	jbd_debug(0, "JBD: recovery, exit status %d, "
		  "recovered transactions %u to %u\n",
		  err, info.start_transaction, info.end_transaction);
	jbd_debug(0, "JBD: Replayed %d and revoked %d/%d blocks\n", 
		  info.nr_replays, info.nr_revoke_hits, info.nr_revokes);

	/* Restart the log at the next transaction ID, thus invalidating
	 * any existing commit records in the log. */
	journal->j_transaction_sequence = ++info.end_transaction;

	journal_clear_revoke(journal);
	sync_blockdev(journal->j_fs_dev);
	return err;
}

/**
 * int journal_skip_recovery() - Start journal and wipe exiting records 
 * @journal: journal to startup
 * 
 * Locate any valid recovery information from the journal and set up the
 * journal structures in memory to ignore it (presumably because the
 * caller has evidence that it is out of date).  
 * This function does'nt appear to be exorted..
 *
 * We perform one pass over the journal to allow us to tell the user how
 * much recovery information is being erased, and to let us initialise
 * the journal transaction sequence numbers to the next unused ID. 
 */
int journal_skip_recovery(journal_t *journal)
{
	int			err;
	journal_superblock_t *	sb;

	struct recovery_info	info;

	memset (&info, 0, sizeof(info));
	sb = journal->j_superblock;

	err = do_one_pass(journal, &info, PASS_SCAN);

	if (err) {
		printk(KERN_ERR "JBD: error %d scanning journal\n", err);
		++journal->j_transaction_sequence;
	} else {
#ifdef CONFIG_JBD_DEBUG
		int dropped = info.end_transaction - be32_to_cpu(sb->s_sequence);
#endif
		jbd_debug(0, 
			  "JBD: ignoring %d transaction%s from the journal.\n",
			  dropped, (dropped == 1) ? "" : "s");
		journal->j_transaction_sequence = ++info.end_transaction;
	}

	journal->j_tail = 0;
	return err;
}

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;

	/* 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))
			       / sizeof(journal_block_tag_t));

	/* 
	 * 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(JFS_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 JFS_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(bh, journal->j_blocksize);
				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 +sizeof(journal_block_tag_t))
			       <= 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 blocknr;

					J_ASSERT(obh != NULL);
					blocknr = be32_to_cpu(tag->t_blocknr);

					/* If the block has been
					 * revoked, then we're all done
					 * here. */
					if (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 & JFS_FLAG_ESCAPE) {
						*((__be32 *)bh->b_data) =
						cpu_to_be32(JFS_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 += sizeof(journal_block_tag_t);
				if (!(flags & JFS_FLAG_SAME_UUID))
					tagp += 16;

				if (flags & JFS_FLAG_LAST_TAG)
					break;
			}

			brelse(bh);
			continue;

		case JFS_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 JFS_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);
			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)
{
	journal_revoke_header_t *header;
	int offset, max;

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

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

		blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
		offset += 4;
		err = journal_set_revoke(journal, blocknr, sequence);
		if (err)
			return err;
		++info->nr_revokes;
	}
	return 0;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/fs/recovery.c
	3	*
	4	* Written by Stephen C. Tweedie <[email protected]>, 1999
	5	*
	6	* Copyright 1999-2000 Red Hat Software --- All Rights Reserved
	7	*
	8	* This file is part of the Linux kernel and is made available under
	9	* the terms of the GNU General Public License, version 2, or at your
	10	* option, any later version, incorporated herein by reference.
	11	*
	12	* Journal recovery routines for the generic filesystem journaling code;
	13	* part of the ext2fs journaling system.
	14	*/
	15
	16	#ifndef __KERNEL__
	17	#include "jfs_user.h"
	18	#else
	19	#include <linux/time.h>
	20	#include <linux/fs.h>
	21	#include <linux/jbd.h>
	22	#include <linux/errno.h>
	23	#include <linux/slab.h>
	24	#endif
	25
	26	/*
	27	* Maintain information about the progress of the recovery job, so that
	28	* the different passes can carry information between them.
	29	*/
	30	struct recovery_info
	31	{
	32	tid_t start_transaction;
	33	tid_t end_transaction;
	34
	35	int nr_replays;
	36	int nr_revokes;
	37	int nr_revoke_hits;
	38	};
	39
	40	enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
	41	static int do_one_pass(journal_t *journal,
	42	struct recovery_info *info, enum passtype pass);
	43	static int scan_revoke_records(journal_t , struct buffer_head ,
	44	tid_t, struct recovery_info *);
	45
	46	#ifdef __KERNEL__
	47
	48	/* Release readahead buffers after use */
	49	void journal_brelse_array(struct buffer_head *b[], int n)
	50	{
	51	while (--n >= 0)
	52	brelse (b[n]);
	53	}
	54
	55
	56	/*
	57	* When reading from the journal, we are going through the block device
	58	* layer directly and so there is no readahead being done for us. We
	59	* need to implement any readahead ourselves if we want it to happen at
	60	* all. Recovery is basically one long sequential read, so make sure we
	61	* do the IO in reasonably large chunks.
	62	*
	63	* This is not so critical that we need to be enormously clever about
	64	* the readahead size, though. 128K is a purely arbitrary, good-enough
65	* fixed value.
66	*/
67
68	#define MAXBUF 8
69	static int do_readahead(journal_t *journal, unsigned int start)
70	{
71	int err;
72	unsigned int max, nbufs, next;
73	unsigned long blocknr;
74	struct buffer_head *bh;
75
76	struct buffer_head * bufs[MAXBUF];
77
78	/* Do up to 128K of readahead */
79	max = start + (128 * 1024 / journal->j_blocksize);
80	if (max > journal->j_maxlen)
81	max = journal->j_maxlen;
82
83	/* Do the readahead itself. We'll submit MAXBUF buffer_heads at
84	* a time to the block device IO layer. */
85
86	nbufs = 0;
87
88	for (next = start; next < max; next++) {
89	err = journal_bmap(journal, next, &blocknr);
90
91	if (err) {
92	printk (KERN_ERR "JBD: bad block at offset %u\n",
93	next);
94	goto failed;
95	}
96
97	bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
98	if (!bh) {
99	err = -ENOMEM;
100	goto failed;
101	}
102
103	if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
104	bufs[nbufs++] = bh;
105	if (nbufs == MAXBUF) {
106	ll_rw_block(READ, nbufs, bufs);
107	journal_brelse_array(bufs, nbufs);
108	nbufs = 0;
109	}
110	} else
111	brelse(bh);
112	}
113
114	if (nbufs)
115	ll_rw_block(READ, nbufs, bufs);
116	err = 0;
117
118	failed:
119	if (nbufs)
120	journal_brelse_array(bufs, nbufs);
121	return err;
122	}
123
124	#endif /* __KERNEL__ */
125
126
127	/*
128	* Read a block from the journal
129	*/
130
131	static int jread(struct buffer_head *bhp, journal_t journal,
132	unsigned int offset)
133	{
134	int err;
135	unsigned long blocknr;
136	struct buffer_head *bh;
137
138	*bhp = NULL;
139
140	if (offset >= journal->j_maxlen) {
141	printk(KERN_ERR "JBD: corrupted journal superblock\n");
142	return -EIO;
143	}
144
145	err = journal_bmap(journal, offset, &blocknr);
146
147	if (err) {
148	printk (KERN_ERR "JBD: bad block at offset %u\n",
149	offset);
150	return err;
151	}
152
153	bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
154	if (!bh)
155	return -ENOMEM;
156
157	if (!buffer_uptodate(bh)) {
158	/* If this is a brand new buffer, start readahead.
159	Otherwise, we assume we are already reading it. */
160	if (!buffer_req(bh))
161	do_readahead(journal, offset);
162	wait_on_buffer(bh);
163	}
164
165	if (!buffer_uptodate(bh)) {
166	printk (KERN_ERR "JBD: Failed to read block at offset %u\n",
167	offset);
168	brelse(bh);
169	return -EIO;
170	}
171
172	*bhp = bh;
173	return 0;
174	}
175
176
177	/*
178	* Count the number of in-use tags in a journal descriptor block.
179	*/
180
181	static int count_tags(struct buffer_head *bh, int size)
182	{
183	char * tagp;
184	journal_block_tag_t * tag;
185	int nr = 0;
186
187	tagp = &bh->b_data[sizeof(journal_header_t)];
188
189	while ((tagp - bh->b_data + sizeof(journal_block_tag_t)) <= size) {
190	tag = (journal_block_tag_t *) tagp;
191
192	nr++;
193	tagp += sizeof(journal_block_tag_t);
194	if (!(tag->t_flags & cpu_to_be32(JFS_FLAG_SAME_UUID)))
195	tagp += 16;
196
197	if (tag->t_flags & cpu_to_be32(JFS_FLAG_LAST_TAG))
198	break;
199	}
200
201	return nr;
202	}
203
204
205	/* Make sure we wrap around the log correctly! */
206	#define wrap(journal, var) \
207	do { \
208	if (var >= (journal)->j_last) \
209	var -= ((journal)->j_last - (journal)->j_first); \
210	} while (0)
211
212	/**
213	* int journal_recover(journal_t *journal) - recovers a on-disk journal
214	* @journal: the journal to recover
215	*
216	* The primary function for recovering the log contents when mounting a
217	* journaled device.
218	*
219	* Recovery is done in three passes. In the first pass, we look for the
220	* end of the log. In the second, we assemble the list of revoke
221	* blocks. In the third and final pass, we replay any un-revoked blocks
222	* in the log.
223	*/
224	int journal_recover(journal_t *journal)
225	{
226	int err;
227	journal_superblock_t * sb;
228
229	struct recovery_info info;
230
231	memset(&info, 0, sizeof(info));
232	sb = journal->j_superblock;
233
234	/*
235	* The journal superblock's s_start field (the current log head)
236	* is always zero if, and only if, the journal was cleanly
237	* unmounted.
238	*/
239
240	if (!sb->s_start) {
241	jbd_debug(1, "No recovery required, last transaction %d\n",
242	be32_to_cpu(sb->s_sequence));
243	journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
244	return 0;
245	}
246
247	err = do_one_pass(journal, &info, PASS_SCAN);
248	if (!err)
249	err = do_one_pass(journal, &info, PASS_REVOKE);
250	if (!err)
251	err = do_one_pass(journal, &info, PASS_REPLAY);
252
253	jbd_debug(0, "JBD: recovery, exit status %d, "
254	"recovered transactions %u to %u\n",
255	err, info.start_transaction, info.end_transaction);
256	jbd_debug(0, "JBD: Replayed %d and revoked %d/%d blocks\n",
257	info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
258
259	/* Restart the log at the next transaction ID, thus invalidating
260	* any existing commit records in the log. */
261	journal->j_transaction_sequence = ++info.end_transaction;
262
263	journal_clear_revoke(journal);
264	sync_blockdev(journal->j_fs_dev);
265	return err;
266	}
267
268	/**
269	* int journal_skip_recovery() - Start journal and wipe exiting records
270	* @journal: journal to startup
271	*
272	* Locate any valid recovery information from the journal and set up the
273	* journal structures in memory to ignore it (presumably because the
274	* caller has evidence that it is out of date).
275	* This function does'nt appear to be exorted..
276	*
277	* We perform one pass over the journal to allow us to tell the user how
278	* much recovery information is being erased, and to let us initialise
279	* the journal transaction sequence numbers to the next unused ID.
280	*/
281	int journal_skip_recovery(journal_t *journal)
282	{
283	int err;
284	journal_superblock_t * sb;
285
286	struct recovery_info info;
287
288	memset (&info, 0, sizeof(info));
289	sb = journal->j_superblock;
290
291	err = do_one_pass(journal, &info, PASS_SCAN);
292
293	if (err) {
294	printk(KERN_ERR "JBD: error %d scanning journal\n", err);
295	++journal->j_transaction_sequence;
296	} else {
297	#ifdef CONFIG_JBD_DEBUG
298	int dropped = info.end_transaction - be32_to_cpu(sb->s_sequence);
299	#endif
300	jbd_debug(0,
301	"JBD: ignoring %d transaction%s from the journal.\n",
302	dropped, (dropped == 1) ? "" : "s");
303	journal->j_transaction_sequence = ++info.end_transaction;
304	}
305
306	journal->j_tail = 0;
307	return err;
308	}
309
310	static int do_one_pass(journal_t *journal,
311	struct recovery_info *info, enum passtype pass)
312	{
313	unsigned int first_commit_ID, next_commit_ID;
314	unsigned long next_log_block;
315	int err, success = 0;
316	journal_superblock_t * sb;
317	journal_header_t * tmp;
318	struct buffer_head * bh;
319	unsigned int sequence;
320	int blocktype;
321
322	/* Precompute the maximum metadata descriptors in a descriptor block */
323	int MAX_BLOCKS_PER_DESC;
324	MAX_BLOCKS_PER_DESC = ((journal->j_blocksize-sizeof(journal_header_t))
325	/ sizeof(journal_block_tag_t));
326
327	/*
328	* First thing is to establish what we expect to find in the log
329	* (in terms of transaction IDs), and where (in terms of log
330	* block offsets): query the superblock.
331	*/
332
333	sb = journal->j_superblock;
334	next_commit_ID = be32_to_cpu(sb->s_sequence);
335	next_log_block = be32_to_cpu(sb->s_start);
336
337	first_commit_ID = next_commit_ID;
338	if (pass == PASS_SCAN)
339	info->start_transaction = first_commit_ID;
340
341	jbd_debug(1, "Starting recovery pass %d\n", pass);
342
343	/*
344	* Now we walk through the log, transaction by transaction,
345	* making sure that each transaction has a commit block in the
346	* expected place. Each complete transaction gets replayed back
347	* into the main filesystem.
348	*/
349
350	while (1) {
351	int flags;
352	char * tagp;
353	journal_block_tag_t * tag;
354	struct buffer_head * obh;
355	struct buffer_head * nbh;
356
357	cond_resched(); /* We're under lock_kernel() */
358
359	/* If we already know where to stop the log traversal,
360	* check right now that we haven't gone past the end of
361	* the log. */
362
363	if (pass != PASS_SCAN)
364	if (tid_geq(next_commit_ID, info->end_transaction))
365	break;
366
367	jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
368	next_commit_ID, next_log_block, journal->j_last);
369
370	/* Skip over each chunk of the transaction looking
371	* either the next descriptor block or the final commit
372	* record. */
373
374	jbd_debug(3, "JBD: checking block %ld\n", next_log_block);
375	err = jread(&bh, journal, next_log_block);
376	if (err)
377	goto failed;
378
379	next_log_block++;
380	wrap(journal, next_log_block);
381
382	/* What kind of buffer is it?
383	*
384	* If it is a descriptor block, check that it has the
385	* expected sequence number. Otherwise, we're all done
386	* here. */
387
388	tmp = (journal_header_t *)bh->b_data;
389
390	if (tmp->h_magic != cpu_to_be32(JFS_MAGIC_NUMBER)) {
391	brelse(bh);
392	break;
393	}
394
395	blocktype = be32_to_cpu(tmp->h_blocktype);
396	sequence = be32_to_cpu(tmp->h_sequence);
397	jbd_debug(3, "Found magic %d, sequence %d\n",
398	blocktype, sequence);
399
400	if (sequence != next_commit_ID) {
401	brelse(bh);
402	break;
403	}
404
405	/* OK, we have a valid descriptor block which matches
406	* all of the sequence number checks. What are we going
407	* to do with it? That depends on the pass... */
408
409	switch(blocktype) {
410	case JFS_DESCRIPTOR_BLOCK:
411	/* If it is a valid descriptor block, replay it
412	* in pass REPLAY; otherwise, just skip over the
413	* blocks it describes. */
414	if (pass != PASS_REPLAY) {
415	next_log_block +=
416	count_tags(bh, journal->j_blocksize);
417	wrap(journal, next_log_block);
418	brelse(bh);
419	continue;
420	}
421
422	/* A descriptor block: we can now write all of
423	* the data blocks. Yay, useful work is finally
424	* getting done here! */
425
426	tagp = &bh->b_data[sizeof(journal_header_t)];
427	while ((tagp - bh->b_data +sizeof(journal_block_tag_t))
428	<= journal->j_blocksize) {
429	unsigned long io_block;
430
431	tag = (journal_block_tag_t *) tagp;
432	flags = be32_to_cpu(tag->t_flags);
433
434	io_block = next_log_block++;
435	wrap(journal, next_log_block);
436	err = jread(&obh, journal, io_block);
437	if (err) {
438	/* Recover what we can, but
439	* report failure at the end. */
440	success = err;
441	printk (KERN_ERR
442	"JBD: IO error %d recovering "
443	"block %ld in log\n",
444	err, io_block);
445	} else {
446	unsigned long blocknr;
447
448	J_ASSERT(obh != NULL);
449	blocknr = be32_to_cpu(tag->t_blocknr);
450
451	/* If the block has been
452	* revoked, then we're all done
453	* here. */
454	if (journal_test_revoke
455	(journal, blocknr,
456	next_commit_ID)) {
457	brelse(obh);
458	++info->nr_revoke_hits;
459	goto skip_write;
460	}
461
462	/* Find a buffer for the new
463	* data being restored */
464	nbh = __getblk(journal->j_fs_dev,
465	blocknr,
466	journal->j_blocksize);
467	if (nbh == NULL) {
468	printk(KERN_ERR
469	"JBD: Out of memory "
470	"during recovery.\n");
471	err = -ENOMEM;
472	brelse(bh);
473	brelse(obh);
474	goto failed;
475	}
476
477	lock_buffer(nbh);
478	memcpy(nbh->b_data, obh->b_data,
479	journal->j_blocksize);
480	if (flags & JFS_FLAG_ESCAPE) {
481	((__be32 )bh->b_data) =
482	cpu_to_be32(JFS_MAGIC_NUMBER);
483	}
484
485	BUFFER_TRACE(nbh, "marking dirty");
486	set_buffer_uptodate(nbh);
487	mark_buffer_dirty(nbh);
488	BUFFER_TRACE(nbh, "marking uptodate");
489	++info->nr_replays;
490	/* ll_rw_block(WRITE, 1, &nbh); */
491	unlock_buffer(nbh);
492	brelse(obh);
493	brelse(nbh);
494	}
495
496	skip_write:
497	tagp += sizeof(journal_block_tag_t);
498	if (!(flags & JFS_FLAG_SAME_UUID))
499	tagp += 16;
500
501	if (flags & JFS_FLAG_LAST_TAG)
502	break;
503	}
504
505	brelse(bh);
506	continue;
507
508	case JFS_COMMIT_BLOCK:
509	/* Found an expected commit block: not much to
510	* do other than move on to the next sequence
511	* number. */
512	brelse(bh);
513	next_commit_ID++;
514	continue;
515
516	case JFS_REVOKE_BLOCK:
517	/* If we aren't in the REVOKE pass, then we can
518	* just skip over this block. */
519	if (pass != PASS_REVOKE) {
520	brelse(bh);
521	continue;
522	}
523
524	err = scan_revoke_records(journal, bh,
525	next_commit_ID, info);
526	brelse(bh);
527	if (err)
528	goto failed;
529	continue;
530
531	default:
532	jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
533	blocktype);
534	goto done;
535	}
536	}
537
538	done:
539	/*
540	* We broke out of the log scan loop: either we came to the
541	* known end of the log or we found an unexpected block in the
542	* log. If the latter happened, then we know that the "current"
543	* transaction marks the end of the valid log.
544	*/
545
546	if (pass == PASS_SCAN)
547	info->end_transaction = next_commit_ID;
548	else {
549	/* It's really bad news if different passes end up at
550	* different places (but possible due to IO errors). */
551	if (info->end_transaction != next_commit_ID) {
552	printk (KERN_ERR "JBD: recovery pass %d ended at "
553	"transaction %u, expected %u\n",
554	pass, next_commit_ID, info->end_transaction);
555	if (!success)
556	success = -EIO;
557	}
558	}
559
560	return success;
561
562	failed:
563	return err;
564	}
565
566
567	/* Scan a revoke record, marking all blocks mentioned as revoked. */
568
569	static int scan_revoke_records(journal_t journal, struct buffer_head bh,
570	tid_t sequence, struct recovery_info *info)
571	{
572	journal_revoke_header_t *header;
573	int offset, max;
574
575	header = (journal_revoke_header_t *) bh->b_data;
576	offset = sizeof(journal_revoke_header_t);
577	max = be32_to_cpu(header->r_count);
578
579	while (offset < max) {
580	unsigned long blocknr;
581	int err;
582
583	blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
584	offset += 4;
585	err = journal_set_revoke(journal, blocknr, sequence);
586	if (err)
587	return err;
588	++info->nr_revokes;
589	}
590	return 0;
591	}