patch-2.4.15 linux/fs/jbd/recovery.c

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diff -u --recursive --new-file v2.4.14/linux/fs/jbd/recovery.c linux/fs/jbd/recovery.c
@@ -0,0 +1,586 @@
+/*
+ * linux/fs/recovery.c
+ * 
+ * Written by Stephen C. Tweedie <sct@redhat.com>, 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/sched.h>
+#include <linux/fs.h>
+#include <linux/jbd.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/locks.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, 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++) {
+		blocknr = journal_bmap(journal, next);
+
+		if (!blocknr) {
+			printk (KERN_ERR "JBD: bad block at offset %u\n",
+				next);
+			err = -EIO;
+			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)
+{
+	unsigned int blocknr;
+	struct buffer_head *bh;
+
+	*bhp = NULL;
+
+	J_ASSERT (offset < journal->j_maxlen);
+	
+	blocknr = journal_bmap(journal, offset);
+
+	if (!blocknr) {
+		printk (KERN_ERR "JBD: bad block at offset %u\n",
+			offset);
+		return -EIO;
+	}
+
+	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 & htonl(JFS_FLAG_SAME_UUID)))
+			tagp += 16;
+
+		if (tag->t_flags & htonl(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)
+
+/*
+ * journal_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",
+			  ntohl(sb->s_sequence));
+		journal->j_transaction_sequence = ntohl(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);
+	fsync_no_super(journal->j_fs_dev);
+	return err;
+}
+
+/*
+ * journal_skip_recovery
+ *
+ * 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).  
+ *
+ * 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 - ntohl(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 = ntohl(sb->s_sequence);
+	next_log_block = ntohl(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;
+		
+		/* 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 != htonl(JFS_MAGIC_NUMBER)) {
+			brelse(bh);
+			break;
+		}
+
+		blocktype = ntohl(tmp->h_blocktype);
+		sequence = ntohl(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 = ntohl(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 = ntohl(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;
+					}
+
+					memcpy(nbh->b_data, obh->b_data,
+							journal->j_blocksize);
+					if (flags & JFS_FLAG_ESCAPE) {
+						*((unsigned int *)bh->b_data) =
+							htonl(JFS_MAGIC_NUMBER);
+					}
+
+					BUFFER_TRACE(nbh, "marking dirty");
+					mark_buffer_dirty(nbh);
+					BUFFER_TRACE(nbh, "marking uptodate");
+					mark_buffer_uptodate(nbh, 1);
+					++info->nr_replays;
+					/* ll_rw_block(WRITE, 1, &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 = ntohl(header->r_count);
+	
+	while (offset < max) {
+		unsigned long blocknr;
+		int err;
+		
+		blocknr = ntohl(* ((unsigned int *) (bh->b_data+offset)));
+		offset += 4;
+		err = journal_set_revoke(journal, blocknr, sequence);
+		if (err)
+			return err;
+		++info->nr_revokes;
+	}
+	return 0;
+}
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