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/*

 * 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;

        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;

        J_ASSERT (offset < journal->j_maxlen);

        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 & 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)

/**

 * 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.

 */

int journal_recover(journal_t *journal)

{

/*

 * 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                     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;

}

/**

 * 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..

 */

int journal_skip_recovery(journal_t *journal)

{

/*

 * 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                     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;

                                        }

                                        lock_buffer(nbh);

                                        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);

                                        unlock_buffer(nbh);

                                        ++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;

}