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![Jan Kara](/assets/img/avatar_default.png)
When we reach cleanup_journal_tail(), there is no guarantee that checkpointed buffers are on a stable storage - especially if buffers were written out by log_do_checkpoint(), they are likely to be only in disk's caches. Thus when we update journal superblock, effectively removing old transaction from journal, this write of superblock can get to stable storage before those checkpointed buffers which can result in filesystem corruption after a crash. A similar problem can happen if we replay the journal and wipe it before flushing disk's caches. Thus we must unconditionally issue a cache flush before we update journal superblock in these cases. The fix is slightly complicated by the fact that we have to get log tail before we issue cache flush but we can store it in the journal superblock only after the cache flush. Otherwise we risk races where new tail is written before appropriate cache flush is finished. I managed to reproduce the corruption using somewhat tweaked Chris Mason's barrier-test scheduler. Also this should fix occasional reports of 'Bit already freed' filesystem errors which are totally unreproducible but inspection of several fs images I've gathered over time points to a problem like this. CC: stable@kernel.org Signed-off-by: Jan Kara <jack@suse.cz>
591 lines
14 KiB
C
591 lines
14 KiB
C
/*
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* linux/fs/jbd/recovery.c
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*
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* Written by Stephen C. Tweedie <sct@redhat.com>, 1999
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*
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* Copyright 1999-2000 Red Hat Software --- All Rights Reserved
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*
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* This file is part of the Linux kernel and is made available under
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* the terms of the GNU General Public License, version 2, or at your
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* option, any later version, incorporated herein by reference.
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*
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* Journal recovery routines for the generic filesystem journaling code;
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* part of the ext2fs journaling system.
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*/
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#ifndef __KERNEL__
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#include "jfs_user.h"
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#else
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#include <linux/time.h>
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#include <linux/fs.h>
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#include <linux/jbd.h>
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#include <linux/errno.h>
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#include <linux/blkdev.h>
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#endif
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/*
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* Maintain information about the progress of the recovery job, so that
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* the different passes can carry information between them.
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*/
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struct recovery_info
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{
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tid_t start_transaction;
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tid_t end_transaction;
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int nr_replays;
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int nr_revokes;
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int nr_revoke_hits;
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};
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enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
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static int do_one_pass(journal_t *journal,
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struct recovery_info *info, enum passtype pass);
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static int scan_revoke_records(journal_t *, struct buffer_head *,
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tid_t, struct recovery_info *);
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#ifdef __KERNEL__
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/* Release readahead buffers after use */
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static void journal_brelse_array(struct buffer_head *b[], int n)
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{
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while (--n >= 0)
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brelse (b[n]);
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}
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/*
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* When reading from the journal, we are going through the block device
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* layer directly and so there is no readahead being done for us. We
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* need to implement any readahead ourselves if we want it to happen at
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* all. Recovery is basically one long sequential read, so make sure we
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* do the IO in reasonably large chunks.
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*
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* This is not so critical that we need to be enormously clever about
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* the readahead size, though. 128K is a purely arbitrary, good-enough
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* fixed value.
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*/
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#define MAXBUF 8
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static int do_readahead(journal_t *journal, unsigned int start)
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{
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int err;
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unsigned int max, nbufs, next;
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unsigned int blocknr;
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struct buffer_head *bh;
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struct buffer_head * bufs[MAXBUF];
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/* Do up to 128K of readahead */
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max = start + (128 * 1024 / journal->j_blocksize);
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if (max > journal->j_maxlen)
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max = journal->j_maxlen;
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/* Do the readahead itself. We'll submit MAXBUF buffer_heads at
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* a time to the block device IO layer. */
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nbufs = 0;
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for (next = start; next < max; next++) {
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err = journal_bmap(journal, next, &blocknr);
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if (err) {
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printk (KERN_ERR "JBD: bad block at offset %u\n",
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next);
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goto failed;
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}
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bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
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if (!bh) {
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err = -ENOMEM;
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goto failed;
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}
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if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
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bufs[nbufs++] = bh;
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if (nbufs == MAXBUF) {
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ll_rw_block(READ, nbufs, bufs);
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journal_brelse_array(bufs, nbufs);
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nbufs = 0;
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}
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} else
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brelse(bh);
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}
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if (nbufs)
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ll_rw_block(READ, nbufs, bufs);
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err = 0;
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failed:
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if (nbufs)
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journal_brelse_array(bufs, nbufs);
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return err;
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}
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#endif /* __KERNEL__ */
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/*
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* Read a block from the journal
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*/
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static int jread(struct buffer_head **bhp, journal_t *journal,
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unsigned int offset)
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{
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int err;
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unsigned int blocknr;
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struct buffer_head *bh;
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*bhp = NULL;
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if (offset >= journal->j_maxlen) {
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printk(KERN_ERR "JBD: corrupted journal superblock\n");
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return -EIO;
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}
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err = journal_bmap(journal, offset, &blocknr);
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if (err) {
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printk (KERN_ERR "JBD: bad block at offset %u\n",
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offset);
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return err;
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}
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bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
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if (!bh)
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return -ENOMEM;
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if (!buffer_uptodate(bh)) {
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/* If this is a brand new buffer, start readahead.
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Otherwise, we assume we are already reading it. */
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if (!buffer_req(bh))
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do_readahead(journal, offset);
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wait_on_buffer(bh);
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}
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if (!buffer_uptodate(bh)) {
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printk (KERN_ERR "JBD: Failed to read block at offset %u\n",
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offset);
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brelse(bh);
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return -EIO;
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}
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*bhp = bh;
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return 0;
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}
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/*
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* Count the number of in-use tags in a journal descriptor block.
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*/
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static int count_tags(struct buffer_head *bh, int size)
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{
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char * tagp;
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journal_block_tag_t * tag;
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int nr = 0;
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tagp = &bh->b_data[sizeof(journal_header_t)];
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while ((tagp - bh->b_data + sizeof(journal_block_tag_t)) <= size) {
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tag = (journal_block_tag_t *) tagp;
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nr++;
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tagp += sizeof(journal_block_tag_t);
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if (!(tag->t_flags & cpu_to_be32(JFS_FLAG_SAME_UUID)))
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tagp += 16;
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if (tag->t_flags & cpu_to_be32(JFS_FLAG_LAST_TAG))
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break;
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}
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return nr;
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}
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/* Make sure we wrap around the log correctly! */
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#define wrap(journal, var) \
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do { \
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if (var >= (journal)->j_last) \
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var -= ((journal)->j_last - (journal)->j_first); \
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} while (0)
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/**
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* journal_recover - recovers a on-disk journal
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* @journal: the journal to recover
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*
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* The primary function for recovering the log contents when mounting a
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* journaled device.
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*
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* Recovery is done in three passes. In the first pass, we look for the
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* end of the log. In the second, we assemble the list of revoke
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* blocks. In the third and final pass, we replay any un-revoked blocks
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* in the log.
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*/
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int journal_recover(journal_t *journal)
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{
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int err, err2;
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journal_superblock_t * sb;
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struct recovery_info info;
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memset(&info, 0, sizeof(info));
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sb = journal->j_superblock;
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/*
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* The journal superblock's s_start field (the current log head)
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* is always zero if, and only if, the journal was cleanly
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* unmounted.
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*/
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if (!sb->s_start) {
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jbd_debug(1, "No recovery required, last transaction %d\n",
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be32_to_cpu(sb->s_sequence));
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journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
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return 0;
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}
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err = do_one_pass(journal, &info, PASS_SCAN);
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if (!err)
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err = do_one_pass(journal, &info, PASS_REVOKE);
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if (!err)
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err = do_one_pass(journal, &info, PASS_REPLAY);
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jbd_debug(1, "JBD: recovery, exit status %d, "
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"recovered transactions %u to %u\n",
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err, info.start_transaction, info.end_transaction);
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jbd_debug(1, "JBD: Replayed %d and revoked %d/%d blocks\n",
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info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
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/* Restart the log at the next transaction ID, thus invalidating
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* any existing commit records in the log. */
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journal->j_transaction_sequence = ++info.end_transaction;
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journal_clear_revoke(journal);
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err2 = sync_blockdev(journal->j_fs_dev);
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if (!err)
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err = err2;
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/* Flush disk caches to get replayed data on the permanent storage */
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if (journal->j_flags & JFS_BARRIER)
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blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
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return err;
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}
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/**
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* journal_skip_recovery - Start journal and wipe exiting records
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* @journal: journal to startup
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*
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* Locate any valid recovery information from the journal and set up the
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* journal structures in memory to ignore it (presumably because the
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* caller has evidence that it is out of date).
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* This function does'nt appear to be exorted..
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*
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* We perform one pass over the journal to allow us to tell the user how
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* much recovery information is being erased, and to let us initialise
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* the journal transaction sequence numbers to the next unused ID.
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*/
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int journal_skip_recovery(journal_t *journal)
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{
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int err;
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struct recovery_info info;
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memset (&info, 0, sizeof(info));
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err = do_one_pass(journal, &info, PASS_SCAN);
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if (err) {
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printk(KERN_ERR "JBD: error %d scanning journal\n", err);
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++journal->j_transaction_sequence;
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} else {
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#ifdef CONFIG_JBD_DEBUG
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int dropped = info.end_transaction -
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be32_to_cpu(journal->j_superblock->s_sequence);
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jbd_debug(1,
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"JBD: ignoring %d transaction%s from the journal.\n",
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dropped, (dropped == 1) ? "" : "s");
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#endif
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journal->j_transaction_sequence = ++info.end_transaction;
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}
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journal->j_tail = 0;
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return err;
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}
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static int do_one_pass(journal_t *journal,
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struct recovery_info *info, enum passtype pass)
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{
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unsigned int first_commit_ID, next_commit_ID;
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unsigned int next_log_block;
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int err, success = 0;
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journal_superblock_t * sb;
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journal_header_t * tmp;
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struct buffer_head * bh;
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unsigned int sequence;
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int blocktype;
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/*
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* First thing is to establish what we expect to find in the log
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* (in terms of transaction IDs), and where (in terms of log
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* block offsets): query the superblock.
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*/
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sb = journal->j_superblock;
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next_commit_ID = be32_to_cpu(sb->s_sequence);
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next_log_block = be32_to_cpu(sb->s_start);
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first_commit_ID = next_commit_ID;
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if (pass == PASS_SCAN)
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info->start_transaction = first_commit_ID;
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jbd_debug(1, "Starting recovery pass %d\n", pass);
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/*
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* Now we walk through the log, transaction by transaction,
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* making sure that each transaction has a commit block in the
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* expected place. Each complete transaction gets replayed back
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* into the main filesystem.
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*/
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while (1) {
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int flags;
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char * tagp;
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journal_block_tag_t * tag;
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struct buffer_head * obh;
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struct buffer_head * nbh;
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cond_resched();
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/* If we already know where to stop the log traversal,
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* check right now that we haven't gone past the end of
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* the log. */
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if (pass != PASS_SCAN)
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if (tid_geq(next_commit_ID, info->end_transaction))
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break;
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jbd_debug(2, "Scanning for sequence ID %u at %u/%u\n",
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next_commit_ID, next_log_block, journal->j_last);
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/* Skip over each chunk of the transaction looking
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* either the next descriptor block or the final commit
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* record. */
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jbd_debug(3, "JBD: checking block %u\n", next_log_block);
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err = jread(&bh, journal, next_log_block);
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if (err)
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goto failed;
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next_log_block++;
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wrap(journal, next_log_block);
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/* What kind of buffer is it?
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*
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* If it is a descriptor block, check that it has the
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* expected sequence number. Otherwise, we're all done
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* here. */
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tmp = (journal_header_t *)bh->b_data;
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if (tmp->h_magic != cpu_to_be32(JFS_MAGIC_NUMBER)) {
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brelse(bh);
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break;
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}
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blocktype = be32_to_cpu(tmp->h_blocktype);
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sequence = be32_to_cpu(tmp->h_sequence);
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jbd_debug(3, "Found magic %d, sequence %d\n",
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blocktype, sequence);
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if (sequence != next_commit_ID) {
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brelse(bh);
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break;
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}
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/* OK, we have a valid descriptor block which matches
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* all of the sequence number checks. What are we going
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* to do with it? That depends on the pass... */
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switch(blocktype) {
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case JFS_DESCRIPTOR_BLOCK:
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/* If it is a valid descriptor block, replay it
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* in pass REPLAY; otherwise, just skip over the
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* blocks it describes. */
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if (pass != PASS_REPLAY) {
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next_log_block +=
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count_tags(bh, journal->j_blocksize);
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wrap(journal, next_log_block);
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brelse(bh);
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continue;
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}
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/* A descriptor block: we can now write all of
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* the data blocks. Yay, useful work is finally
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* getting done here! */
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tagp = &bh->b_data[sizeof(journal_header_t)];
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while ((tagp - bh->b_data +sizeof(journal_block_tag_t))
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<= journal->j_blocksize) {
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unsigned int io_block;
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tag = (journal_block_tag_t *) tagp;
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flags = be32_to_cpu(tag->t_flags);
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io_block = next_log_block++;
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wrap(journal, next_log_block);
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err = jread(&obh, journal, io_block);
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if (err) {
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/* Recover what we can, but
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* report failure at the end. */
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success = err;
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printk (KERN_ERR
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"JBD: IO error %d recovering "
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"block %u in log\n",
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err, io_block);
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} else {
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unsigned int blocknr;
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J_ASSERT(obh != NULL);
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blocknr = be32_to_cpu(tag->t_blocknr);
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/* If the block has been
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* revoked, then we're all done
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* here. */
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if (journal_test_revoke
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(journal, blocknr,
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next_commit_ID)) {
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brelse(obh);
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++info->nr_revoke_hits;
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goto skip_write;
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}
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/* Find a buffer for the new
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* data being restored */
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nbh = __getblk(journal->j_fs_dev,
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blocknr,
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journal->j_blocksize);
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if (nbh == NULL) {
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printk(KERN_ERR
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"JBD: Out of memory "
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"during recovery.\n");
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err = -ENOMEM;
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brelse(bh);
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brelse(obh);
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goto failed;
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}
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lock_buffer(nbh);
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memcpy(nbh->b_data, obh->b_data,
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journal->j_blocksize);
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if (flags & JFS_FLAG_ESCAPE) {
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*((__be32 *)nbh->b_data) =
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cpu_to_be32(JFS_MAGIC_NUMBER);
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}
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BUFFER_TRACE(nbh, "marking dirty");
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set_buffer_uptodate(nbh);
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mark_buffer_dirty(nbh);
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BUFFER_TRACE(nbh, "marking uptodate");
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++info->nr_replays;
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/* ll_rw_block(WRITE, 1, &nbh); */
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unlock_buffer(nbh);
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brelse(obh);
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brelse(nbh);
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}
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skip_write:
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tagp += sizeof(journal_block_tag_t);
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if (!(flags & JFS_FLAG_SAME_UUID))
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tagp += 16;
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if (flags & JFS_FLAG_LAST_TAG)
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break;
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}
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brelse(bh);
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continue;
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case JFS_COMMIT_BLOCK:
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/* Found an expected commit block: not much to
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* do other than move on to the next sequence
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* number. */
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brelse(bh);
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next_commit_ID++;
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continue;
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case JFS_REVOKE_BLOCK:
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/* If we aren't in the REVOKE pass, then we can
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* just skip over this block. */
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if (pass != PASS_REVOKE) {
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brelse(bh);
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continue;
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}
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err = scan_revoke_records(journal, bh,
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next_commit_ID, info);
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brelse(bh);
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if (err)
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goto failed;
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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)
|
|
{
|
|
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 int 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;
|
|
}
|