/*
* linux/fs/checkpoint.c
*
* Written by Stephen C. Tweedie <sct@redhat.com>, 1999
*
* Copyright 1999 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.
*
* Checkpoint routines for the generic filesystem journaling code.
* Part of the ext2fs journaling system.
*
* Checkpointing is the process of ensuring that a section of the log is
* committed fully to disk, so that that portion of the log can be
* reused.
*/
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd.h>
#include <linux/errno.h>
#include <linux/slab.h>
/*
* Unlink a buffer from a transaction.
*
* Called with j_list_lock held.
*/
static inline void __buffer_unlink(struct journal_head *jh)
{
transaction_t *transaction;
transaction = jh->b_cp_transaction;
jh->b_cp_transaction = NULL;
jh->b_cpnext->b_cpprev = jh->b_cpprev;
jh->b_cpprev->b_cpnext = jh->b_cpnext;
if (transaction->t_checkpoint_list == jh)
transaction->t_checkpoint_list = jh->b_cpnext;
if (transaction->t_checkpoint_list == jh)
transaction->t_checkpoint_list = NULL;
}
/*
* Try to release a checkpointed buffer from its transaction.
* Returns 1 if we released it.
* Requires j_list_lock
* Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
*/
static int __try_to_free_cp_buf(struct journal_head *jh)
{
int ret = 0;
struct buffer_head *bh = jh2bh(jh);
if (jh->b_jlist == BJ_None && !buffer_locked(bh) && !buffer_dirty(bh)) {
JBUFFER_TRACE(jh, "remove from checkpoint list");
__journal_remove_checkpoint(jh);
jbd_unlock_bh_state(bh);
journal_remove_journal_head(bh);
BUFFER_TRACE(bh, "release");
__brelse(bh);
ret = 1;
} else {
jbd_unlock_bh_state(bh);
}
return ret;
}
/*
* __log_wait_for_space: wait until there is space in the journal.
*
* Called under j-state_lock *only*. It will be unlocked if we have to wait
* for a checkpoint to free up some space in the log.
*/
void __log_wait_for_space(journal_t *journal)
{
int nblocks;
assert_spin_locked(&journal->j_state_lock);
nblocks = jbd_space_needed(journal);
while (__log_space_left(journal) < nblocks) {
if (journal->j_flags & JFS_ABORT)
return;
spin_unlock(&journal->j_state_lock);
down(&journal->j_checkpoint_sem);
/*
* Test again, another process may have checkpointed while we
* were waiting for the checkpoint lock
*/
spin_lock(&journal->j_state_lock);
nblocks = jbd_space_needed(journal);
if (__log_space_left(journal) < nblocks) {
spin_unlock(&journal->j_state_lock);
log_do_checkpoint(journal);
spin_lock(&journal->j_state_lock);
}
up(&journal->j_checkpoint_sem);
}
}
/*
* We were unable to perform jbd_trylock_bh_state() inside j_list_lock.
* The caller must restart a list walk. Wait for someone else to run
* jbd_unlock_bh_state().
*/
static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)
{
get_bh(bh);
spin_unlock(&journal->j_list_lock);
jbd_lock_bh_state(bh);
jbd_unlock_bh_state(bh);
put_bh(bh);
}
/*
* Clean up a transaction's checkpoint list.
*
* We wait for any pending IO to complete and make sure any clean
* buffers are removed from the transaction.
*
* Return 1 if we performed any actions which might have destroyed the
* checkpoint. (journal_remove_checkpoint() deletes the transaction when
* the last checkpoint buffer is cleansed)
*
* Called with j_list_lock held.
*/
static int __cleanup_transaction(journal_t *journal, transaction_t *transaction)
{
struct journal_head *jh, *next_jh, *last_jh;
struct buffer_head *bh;
int ret = 0;
assert_spin_locked(&journal->j_list_lock);
jh = transaction->t_checkpoint_list;
if (!jh)
return 0;
last_jh = jh->b_cpprev;
next_jh = jh;
do {
jh = next_jh;
bh = jh2bh(jh);
if (buffer_locked(bh)) {
atomic_inc(&bh->b_count);
spin_unlock(&journal->j_list_lock);
wait_on_buffer(bh);
/* the journal_head may have gone by now */
BUFFER_TRACE(bh, "brelse");
__brelse(bh);
goto out_return_1;
}
/*
* This is foul
*/
if (!jbd_trylock_bh_state(bh)) {
jbd_sync_bh(journal, bh);
goto out_return_1;
}
if (jh->b_transaction != NULL) {
transaction_t *t = jh->b_transaction;
tid_t tid = t->t_tid;
spin_unlock(&journal->j_list_lock);
jbd_unlock_bh_state(bh);
log_start_commit(journal, tid);
log_wait_commit(journal, tid);
goto out_return_1;
}
/*
* AKPM: I think the buffer_jbddirty test is redundant - it
* shouldn't have NULL b_transaction?
*/
next_jh = jh->b_cpnext;
if (!buffer_dirty(bh) && !buffer_jbddirty(bh)) {
BUFFER_TRACE(bh, "remove from checkpoint");
__journal_remove_checkpoint(jh);
jbd_unlock_bh_state(bh);
journal_remove_journal_head(bh);
__brelse(bh);
ret = 1;
} else {
jbd_unlock_bh_state(bh);
}
} while (jh != last_jh);
return ret;
out_return_1:
spin_lock(&journal->j_list_lock);
return 1;
}
#define NR_BATCH 64
static void
__flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
{
int i;
spin_unlock(&journal->j_list_lock);
ll_rw_block(WRITE, *batch_count, bhs);
spin_lock(&journal->j_list_lock);
for (i = 0; i < *batch_count; i++) {
struct buffer_head *bh = bhs[i];
clear_buffer_jwrite(bh);
BUFFER_TRACE(bh, "brelse");
__brelse(bh);
}
*batch_count = 0;
}
/*
* Try to flush one buffer from the checkpoint list to disk.
*
* Return 1 if something happened which requires us to abort the current
* scan of the checkpoint list.
*
* Called with j_list_lock held.
* Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
*/
static int __flush_buffer(journal_t *journal, struct journal_head *jh,
struct buffer_head **bhs, int *batch_count,
int *drop_count)
{
struct buffer_head *bh = jh2bh(jh);
int ret = 0;
if (buffer_dirty(bh) && !buffer_locked(bh) && jh->b_jlist == BJ_None) {
J_ASSERT_JH(jh, jh->b_transaction == NULL);
/*
* Important: we are about to write the buffer, and
* possibly block, while still holding the journal lock.
* We cannot afford to let the transaction logic start
* messing around with this buffer before we write it to
* disk, as that would break recoverability.
*/
BUFFER_TRACE(bh, "queue");
get_bh(bh);
J_ASSERT_BH(bh, !buffer_jwrite(bh));
set_buffer_jwrite(bh);
bhs[*batch_count] = bh;
jbd_unlock_bh_state(bh);
(*batch_count)++;
if (*batch_count == NR_BATCH) {
__flush_batch(journal, bhs, batch_count);
ret = 1;
}
} else {
int last_buffer = 0;
if (jh->b_cpnext == jh) {
/* We may be about to drop the transaction. Tell the
* caller that the lists have changed.
*/
last_buffer = 1;
}
if (__try_to_free_cp_buf(jh)) {
(*drop_count)++;
ret = last_buffer;
}
}
return ret;
}
/*
* Perform an actual checkpoint. We don't write out only enough to
* satisfy the current blocked requests: rather we submit a reasonably
* sized chunk of the outstanding data to disk at once for
* efficiency. __log_wait_for_space() will retry if we didn't free enough.
*
* However, we _do_ take into account the amount requested so that once
* the IO has been queued, we can return as soon as enough of it has
* completed to disk.
*
* The journal should be locked before calling this function.
*/
int log_do_checkpoint(journal_t *journal)
{
int result;
int batch_count = 0;
struct buffer_head *bhs[NR_BATCH];
jbd_debug(1, "Start checkpoint\n");
/*
* First thing: if there are any transactions in the log which
* don't need checkpointing, just eliminate them from the
* journal straight away.
*/
result = cleanup_journal_tail(journal);
jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
if (result <= 0)
return result;
/*
* OK, we need to start writing disk blocks. Try to free up a
* quarter of the log in a single checkpoint if we can.
*/
/*
* AKPM: check this code. I had a feeling a while back that it
* degenerates into a busy loop at unmount time.
*/
spin_lock(&journal->j_list_lock);
while (journal->j_checkpoint_transactions) {
transaction_t *transaction;
struct journal_head *jh, *last_jh, *next_jh;
int drop_count = 0;
int cleanup_ret, retry = 0;
tid_t this_tid;
transaction = journal->j_checkpoint_transactions;
this_tid = transaction->t_tid;
jh = transaction->t_checkpoint_list;
last_jh = jh->b_cpprev;
next_jh = jh;
do {
struct buffer_head *bh;
jh = next_jh;
next_jh = jh->b_cpnext;
bh = jh2bh(jh);
if (!jbd_trylock_bh_state(bh)) {
jbd_sync_bh(journal, bh);
spin_lock(&journal->j_list_lock);
retry = 1;
break;
}
retry = __flush_buffer(journal, jh, bhs, &batch_count, &drop_count);
if (cond_resched_lock(&journal->j_list_lock)) {
retry = 1;
break;
}
} while (jh != last_jh && !retry);
if (batch_count) {
__flush_batch(journal, bhs, &batch_count);
retry = 1;
}
/*
* If someone cleaned up this transaction while we slept, we're
* done
*/
if (journal->j_checkpoint_transactions != transaction)
break;
if (retry)
continue;
/*
* Maybe it's a new transaction, but it fell at the same
* address
*/
if (transaction->t_tid != this_tid)
continue;
/*
* We have walked the whole transaction list without
* finding anything to write to disk. We had better be
* able to make some progress or we are in trouble.
*/
cleanup_ret = __cleanup_transaction(journal, transaction);
J_ASSERT(drop_count != 0 || cleanup_ret != 0);
if (journal->j_checkpoint_transactions != transaction)
break;
}
spin_unlock(&journal->j_list_lock);
result = cleanup_journal_tail(journal);
if (result < 0)
return result;
return 0;
}
/*
* Check the list of checkpoint transactions for the journal to see if
* we have already got rid of any since the last update of the log tail
* in the journal superblock. If so, we can instantly roll the
* superblock forward to remove those transactions from the log.
*
* Return <0 on error, 0 on success, 1 if there was nothing to clean up.
*
* Called with the journal lock held.
*
* This is the only part of the journaling code which really needs to be
* aware of transaction aborts. Checkpointing involves writing to the
* main filesystem area rather than to the journal, so it can proceed
* even in abort state, but we must not update the journal superblock if
* we have an abort error outstanding.
*/
int cleanup_journal_tail(journal_t *journal)
{
transaction_t * transaction;
tid_t first_tid;
unsigned long blocknr, freed;
/* OK, work out the oldest transaction remaining in the log, and
* the log block it starts at.
*
* If the log is now empty, we need to work out which is the
* next transaction ID we will write, and where it will
* start. */
spin_lock(&journal->j_state_lock);
spin_lock(&journal->j_list_lock);
transaction = journal->j_checkpoint_transactions;
if (transaction) {
first_tid = transaction->t_tid;
blocknr = transaction->t_log_start;
} else if ((transaction = journal->j_committing_transaction) != NULL) {
first_tid = transaction->t_tid;
blocknr = transaction->t_log_start;
} else if ((transaction = journal->j_running_transaction) != NULL) {
first_tid = transaction->t_tid;
blocknr = journal->j_head;
} else {
first_tid = journal->j_transaction_sequence;
blocknr = journal->j_head;
}
spin_unlock(&journal->j_list_lock);
J_ASSERT(blocknr != 0);
/* If the oldest pinned transaction is at the tail of the log
already then there's not much we can do right now. */
if (journal->j_tail_sequence == first_tid) {
spin_unlock(&journal->j_state_lock);
return 1;
}
/* OK, update the superblock to recover the freed space.
* Physical blocks come first: have we wrapped beyond the end of
* the log? */
freed = blocknr - journal->j_tail;
if (blocknr < journal->j_tail)
freed = freed + journal->j_last - journal->j_first;
jbd_debug(1,
"Cleaning journal tail from %d to %d (offset %lu), "
"freeing %lu\n",
journal->j_tail_sequence, first_tid, blocknr, freed);
journal->j_free += freed;
journal->j_tail_sequence = first_tid;
journal->j_tail = blocknr;
spin_unlock(&journal->j_state_lock);
if (!(journal->j_flags & JFS_ABORT))
journal_update_superblock(journal, 1);
return 0;
}
/* Checkpoint list management */
/*
* journal_clean_checkpoint_list
*
* Find all the written-back checkpoint buffers in the journal and release them.
*
* Called with the journal locked.
* Called with j_list_lock held.
* Returns number of bufers reaped (for debug)
*/
int __journal_clean_checkpoint_list(journal_t *journal)
{
transaction_t *transaction, *last_transaction, *next_transaction;
int ret = 0;
transaction = journal->j_checkpoint_transactions;
if (transaction == 0)
goto out;
last_transaction = transaction->t_cpprev;
next_transaction = transaction;
do {
struct journal_head *jh;
transaction = next_transaction;
next_transaction = transaction->t_cpnext;
jh = transaction->t_checkpoint_list;
if (jh) {
struct journal_head *last_jh = jh->b_cpprev;
struct journal_head *next_jh = jh;
do {
jh = next_jh;
next_jh = jh->b_cpnext;
/* Use trylock because of the ranknig */
if (jbd_trylock_bh_state(jh2bh(jh)))
ret += __try_to_free_cp_buf(jh);
/*
* This function only frees up some memory
* if possible so we dont have an obligation
* to finish processing. Bail out if preemption
* requested:
*/
if (need_resched())
goto out;
} while (jh != last_jh);
}
} while (transaction != last_transaction);
out:
return ret;
}
/*
* journal_remove_checkpoint: called after a buffer has been committed
* to disk (either by being write-back flushed to disk, or being
* committed to the log).
*
* We cannot safely clean a transaction out of the log until all of the
* buffer updates committed in that transaction have safely been stored
* elsewhere on disk. To achieve this, all of the buffers in a
* transaction need to be maintained on the transaction's checkpoint
* list until they have been rewritten, at which point this function is
* called to remove the buffer from the existing transaction's
* checkpoint list.
*
* This function is called with the journal locked.
* This function is called with j_list_lock held.
*/
void __journal_remove_checkpoint(struct journal_head *jh)
{
transaction_t *transaction;
journal_t *journal;
JBUFFER_TRACE(jh, "entry");
if ((transaction = jh->b_cp_transaction) == NULL) {
JBUFFER_TRACE(jh, "not on transaction");
goto out;
}
journal = transaction->t_journal;
__buffer_unlink(jh);
if (transaction->t_checkpoint_list != NULL)
goto out;
JBUFFER_TRACE(jh, "transaction has no more buffers");
/*
* There is one special case to worry about: if we have just pulled the
* buffer off a committing transaction's forget list, then even if the
* checkpoint list is empty, the transaction obviously cannot be
* dropped!
*
* The locking here around j_committing_transaction is a bit sleazy.
* See the comment at the end of journal_commit_transaction().
*/
if (transaction == journal->j_committing_transaction) {
JBUFFER_TRACE(jh, "belongs to committing transaction");
goto out;
}
/* OK, that was the last buffer for the transaction: we can now
safely remove this transaction from the log */
__journal_drop_transaction(journal, transaction);
/* Just in case anybody was waiting for more transactions to be
checkpointed... */
wake_up(&journal->j_wait_logspace);
out:
JBUFFER_TRACE(jh, "exit");
}
/*
* journal_insert_checkpoint: put a committed buffer onto a checkpoint
* list so that we know when it is safe to clean the transaction out of
* the log.
*
* Called with the journal locked.
* Called with j_list_lock held.
*/
void __journal_insert_checkpoint(struct journal_head *jh,
transaction_t *transaction)
{
JBUFFER_TRACE(jh, "entry");
J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
jh->b_cp_transaction = transaction;
if (!transaction->t_checkpoint_list) {
jh->b_cpnext = jh->b_cpprev = jh;
} else {
jh->b_cpnext = transaction->t_checkpoint_list;
jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
jh->b_cpprev->b_cpnext = jh;
jh->b_cpnext->b_cpprev = jh;
}
transaction->t_checkpoint_list = jh;
}
/*
* We've finished with this transaction structure: adios...
*
* The transaction must have no links except for the checkpoint by this
* point.
*
* Called with the journal locked.
* Called with j_list_lock held.
*/
void __journal_drop_transaction(journal_t *journal, transaction_t *transaction)
{
assert_spin_locked(&journal->j_list_lock);
if (transaction->t_cpnext) {
transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
if (journal->j_checkpoint_transactions == transaction)
journal->j_checkpoint_transactions =
transaction->t_cpnext;
if (journal->j_checkpoint_transactions == transaction)
journal->j_checkpoint_transactions = NULL;
}
J_ASSERT(transaction->t_state == T_FINISHED);
J_ASSERT(transaction->t_buffers == NULL);
J_ASSERT(transaction->t_sync_datalist == NULL);
J_ASSERT(transaction->t_forget == NULL);
J_ASSERT(transaction->t_iobuf_list == NULL);
J_ASSERT(transaction->t_shadow_list == NULL);
J_ASSERT(transaction->t_log_list == NULL);
J_ASSERT(transaction->t_checkpoint_list == NULL);
J_ASSERT(transaction->t_updates == 0);
J_ASSERT(journal->j_committing_transaction != transaction);
J_ASSERT(journal->j_running_transaction != transaction);
jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
kfree(transaction);
}
