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DEFINITIONS
This source file includes following definitions.
- journal_brelse_array
- do_readahead
- jread
- count_tags
- jbd2_journal_recover
- jbd2_journal_skip_recovery
- read_tag_block
- calc_chksums
- do_one_pass
- scan_revoke_records
/*
* linux/fs/jbd2/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/time.h>
#include <linux/fs.h>
#include <linux/jbd2.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/crc32.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 */
static 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 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 = jbd2_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 long blocknr;
struct buffer_head *bh;
*bhp = NULL;
if (offset >= journal->j_maxlen) {
printk(KERN_ERR "JBD: corrupted journal superblock\n");
return -EIO;
}
err = jbd2_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(journal_t *journal, struct buffer_head *bh)
{
char * tagp;
journal_block_tag_t * tag;
int nr = 0, size = journal->j_blocksize;
int tag_bytes = journal_tag_bytes(journal);
tagp = &bh->b_data[sizeof(journal_header_t)];
while ((tagp - bh->b_data + tag_bytes) <= size) {
tag = (journal_block_tag_t *) tagp;
nr++;
tagp += tag_bytes;
if (!(tag->t_flags & cpu_to_be32(JBD2_FLAG_SAME_UUID)))
tagp += 16;
if (tag->t_flags & cpu_to_be32(JBD2_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)
/**
* jbd2_journal_recover - 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 jbd2_journal_recover(journal_t *journal)
{
int err, err2;
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(1, "JBD: recovery, exit status %d, "
"recovered transactions %u to %u\n",
err, info.start_transaction, info.end_transaction);
jbd_debug(1, "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;
jbd2_journal_clear_revoke(journal);
err2 = sync_blockdev(journal->j_fs_dev);
if (!err)
err = err2;
return err;
}
/**
* jbd2_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 jbd2_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_JBD2_DEBUG
int dropped = info.end_transaction - be32_to_cpu(sb->s_sequence);
#endif
jbd_debug(1,
"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 inline unsigned long long read_tag_block(int tag_bytes, journal_block_tag_t *tag)
{
unsigned long long block = be32_to_cpu(tag->t_blocknr);
if (tag_bytes > JBD2_TAG_SIZE32)
block |= (u64)be32_to_cpu(tag->t_blocknr_high) << 32;
return block;
}
/*
* calc_chksums calculates the checksums for the blocks described in the
* descriptor block.
*/
static int calc_chksums(journal_t *journal, struct buffer_head *bh,
unsigned long *next_log_block, __u32 *crc32_sum)
{
int i, num_blks, err;
unsigned long io_block;
struct buffer_head *obh;
num_blks = count_tags(journal, bh);
/* Calculate checksum of the descriptor block. */
*crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);
for (i = 0; i < num_blks; i++) {
io_block = (*next_log_block)++;
wrap(journal, *next_log_block);
err = jread(&obh, journal, io_block);
if (err) {
printk(KERN_ERR "JBD: IO error %d recovering block "
"%lu in log\n", err, io_block);
return 1;
} else {
*crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
obh->b_size);
}
put_bh(obh);
}
return 0;
}
static int do_one_pass(journal_t *journal,
struct recovery_info *info, enum passtype pass)
{
unsigned int first_commit_ID, next_commit_ID;
unsigned long next_log_block;
int err, success = 0;
journal_superblock_t * sb;
journal_header_t * tmp;
struct buffer_head * bh;
unsigned int sequence;
int blocktype;
int tag_bytes = journal_tag_bytes(journal);
__u32 crc32_sum = ~0; /* Transactional Checksums */
/* Precompute the maximum metadata descriptors in a descriptor block */
int MAX_BLOCKS_PER_DESC;
MAX_BLOCKS_PER_DESC = ((journal->j_blocksize-sizeof(journal_header_t))
/ tag_bytes);
/*
* First thing is to establish what we expect to find in the log
* (in terms of transaction IDs), and where (in terms of log
* block offsets): query the superblock.
*/
sb = journal->j_superblock;
next_commit_ID = be32_to_cpu(sb->s_sequence);
next_log_block = be32_to_cpu(sb->s_start);
first_commit_ID = next_commit_ID;
if (pass == PASS_SCAN)
info->start_transaction = first_commit_ID;
jbd_debug(1, "Starting recovery pass %d\n", pass);
/*
* Now we walk through the log, transaction by transaction,
* making sure that each transaction has a commit block in the
* expected place. Each complete transaction gets replayed back
* into the main filesystem.
*/
while (1) {
int flags;
char * tagp;
journal_block_tag_t * tag;
struct buffer_head * obh;
struct buffer_head * nbh;
cond_resched();
/* If we already know where to stop the log traversal,
* check right now that we haven't gone past the end of
* the log. */
if (pass != PASS_SCAN)
if (tid_geq(next_commit_ID, info->end_transaction))
break;
jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
next_commit_ID, next_log_block, journal->j_last);
/* Skip over each chunk of the transaction looking
* either the next descriptor block or the final commit
* record. */
jbd_debug(3, "JBD: checking block %ld\n", next_log_block);
err = jread(&bh, journal, next_log_block);
if (err)
goto failed;
next_log_block++;
wrap(journal, next_log_block);
/* What kind of buffer is it?
*
* If it is a descriptor block, check that it has the
* expected sequence number. Otherwise, we're all done
* here. */
tmp = (journal_header_t *)bh->b_data;
if (tmp->h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER)) {
brelse(bh);
break;
}
blocktype = be32_to_cpu(tmp->h_blocktype);
sequence = be32_to_cpu(tmp->h_sequence);
jbd_debug(3, "Found magic %d, sequence %d\n",
blocktype, sequence);
if (sequence != next_commit_ID) {
brelse(bh);
break;
}
/* OK, we have a valid descriptor block which matches
* all of the sequence number checks. What are we going
* to do with it? That depends on the pass... */
switch(blocktype) {
case JBD2_DESCRIPTOR_BLOCK:
/* If it is a valid descriptor block, replay it
* in pass REPLAY; if journal_checksums enabled, then
* calculate checksums in PASS_SCAN, otherwise,
* just skip over the blocks it describes. */
if (pass != PASS_REPLAY) {
if (pass == PASS_SCAN &&
JBD2_HAS_COMPAT_FEATURE(journal,
JBD2_FEATURE_COMPAT_CHECKSUM) &&
!info->end_transaction) {
if (calc_chksums(journal, bh,
&next_log_block,
&crc32_sum)) {
put_bh(bh);
break;
}
put_bh(bh);
continue;
}
next_log_block += count_tags(journal, bh);
wrap(journal, next_log_block);
put_bh(bh);
continue;
}
/* A descriptor block: we can now write all of
* the data blocks. Yay, useful work is finally
* getting done here! */
tagp = &bh->b_data[sizeof(journal_header_t)];
while ((tagp - bh->b_data + tag_bytes)
<= journal->j_blocksize) {
unsigned long io_block;
tag = (journal_block_tag_t *) tagp;
flags = be32_to_cpu(tag->t_flags);
io_block = next_log_block++;
wrap(journal, next_log_block);
err = jread(&obh, journal, io_block);
if (err) {
/* Recover what we can, but
* report failure at the end. */
success = err;
printk (KERN_ERR
"JBD: IO error %d recovering "
"block %ld in log\n",
err, io_block);
} else {
unsigned long long blocknr;
J_ASSERT(obh != NULL);
blocknr = read_tag_block(tag_bytes,
tag);
/* If the block has been
* revoked, then we're all done
* here. */
if (jbd2_journal_test_revoke
(journal, blocknr,
next_commit_ID)) {
brelse(obh);
++info->nr_revoke_hits;
goto skip_write;
}
/* Find a buffer for the new
* data being restored */
nbh = __getblk(journal->j_fs_dev,
blocknr,
journal->j_blocksize);
if (nbh == NULL) {
printk(KERN_ERR
"JBD: Out of memory "
"during recovery.\n");
err = -ENOMEM;
brelse(bh);
brelse(obh);
goto failed;
}
lock_buffer(nbh);
memcpy(nbh->b_data, obh->b_data,
journal->j_blocksize);
if (flags & JBD2_FLAG_ESCAPE) {
*((__be32 *)nbh->b_data) =
cpu_to_be32(JBD2_MAGIC_NUMBER);
}
BUFFER_TRACE(nbh, "marking dirty");
set_buffer_uptodate(nbh);
mark_buffer_dirty(nbh);
BUFFER_TRACE(nbh, "marking uptodate");
++info->nr_replays;
/* ll_rw_block(WRITE, 1, &nbh); */
unlock_buffer(nbh);
brelse(obh);
brelse(nbh);
}
skip_write:
tagp += tag_bytes;
if (!(flags & JBD2_FLAG_SAME_UUID))
tagp += 16;
if (flags & JBD2_FLAG_LAST_TAG)
break;
}
brelse(bh);
continue;
case JBD2_COMMIT_BLOCK:
/* How to differentiate between interrupted commit
* and journal corruption ?
*
* {nth transaction}
* Checksum Verification Failed
* |
* ____________________
* | |
* async_commit sync_commit
* | |
* | GO TO NEXT "Journal Corruption"
* | TRANSACTION
* |
* {(n+1)th transanction}
* |
* _______|______________
* | |
* Commit block found Commit block not found
* | |
* "Journal Corruption" |
* _____________|_________
* | |
* nth trans corrupt OR nth trans
* and (n+1)th interrupted interrupted
* before commit block
* could reach the disk.
* (Cannot find the difference in above
* mentioned conditions. Hence assume
* "Interrupted Commit".)
*/
/* Found an expected commit block: if checksums
* are present verify them in PASS_SCAN; else not
* much to do other than move on to the next sequence
* number. */
if (pass == PASS_SCAN &&
JBD2_HAS_COMPAT_FEATURE(journal,
JBD2_FEATURE_COMPAT_CHECKSUM)) {
int chksum_err, chksum_seen;
struct commit_header *cbh =
(struct commit_header *)bh->b_data;
unsigned found_chksum =
be32_to_cpu(cbh->h_chksum[0]);
chksum_err = chksum_seen = 0;
if (info->end_transaction) {
journal->j_failed_commit =
info->end_transaction;
brelse(bh);
break;
}
if (crc32_sum == found_chksum &&
cbh->h_chksum_type == JBD2_CRC32_CHKSUM &&
cbh->h_chksum_size ==
JBD2_CRC32_CHKSUM_SIZE)
chksum_seen = 1;
else if (!(cbh->h_chksum_type == 0 &&
cbh->h_chksum_size == 0 &&
found_chksum == 0 &&
!chksum_seen))
/*
* If fs is mounted using an old kernel and then
* kernel with journal_chksum is used then we
* get a situation where the journal flag has
* checksum flag set but checksums are not
* present i.e chksum = 0, in the individual
* commit blocks.
* Hence to avoid checksum failures, in this
* situation, this extra check is added.
*/
chksum_err = 1;
if (chksum_err) {
info->end_transaction = next_commit_ID;
if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)){
journal->j_failed_commit =
next_commit_ID;
brelse(bh);
break;
}
}
crc32_sum = ~0;
}
brelse(bh);
next_commit_ID++;
continue;
case JBD2_REVOKE_BLOCK:
/* If we aren't in the REVOKE pass, then we can
* just skip over this block. */
if (pass != PASS_REVOKE) {
brelse(bh);
continue;
}
err = scan_revoke_records(journal, bh,
next_commit_ID, info);
brelse(bh);
if (err)
goto failed;
continue;
default:
jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
blocktype);
brelse(bh);
goto done;
}
}
done:
/*
* We broke out of the log scan loop: either we came to the
* known end of the log or we found an unexpected block in the
* log. If the latter happened, then we know that the "current"
* transaction marks the end of the valid log.
*/
if (pass == PASS_SCAN) {
if (!info->end_transaction)
info->end_transaction = next_commit_ID;
} else {
/* It's really bad news if different passes end up at
* different places (but possible due to IO errors). */
if (info->end_transaction != next_commit_ID) {
printk (KERN_ERR "JBD: recovery pass %d ended at "
"transaction %u, expected %u\n",
pass, next_commit_ID, info->end_transaction);
if (!success)
success = -EIO;
}
}
return success;
failed:
return err;
}
/* Scan a revoke record, marking all blocks mentioned as revoked. */
static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
tid_t sequence, struct recovery_info *info)
{
jbd2_journal_revoke_header_t *header;
int offset, max;
int record_len = 4;
header = (jbd2_journal_revoke_header_t *) bh->b_data;
offset = sizeof(jbd2_journal_revoke_header_t);
max = be32_to_cpu(header->r_count);
if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
record_len = 8;
while (offset + record_len <= max) {
unsigned long long blocknr;
int err;
if (record_len == 4)
blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
else
blocknr = be64_to_cpu(* ((__be64 *) (bh->b_data+offset)));
offset += record_len;
err = jbd2_journal_set_revoke(journal, blocknr, sequence);
if (err)
return err;
++info->nr_revokes;
}
return 0;
}