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DEFINITIONS
This source file includes following definitions.
- __buffer_unlink_first
- __buffer_unlink
- __buffer_relink_io
- __try_to_free_cp_buf
- __log_wait_for_space
- jbd_sync_bh
- __wait_cp_io
- __flush_batch
- __process_buffer
- log_do_checkpoint
- cleanup_journal_tail
- journal_clean_one_cp_list
- __journal_clean_checkpoint_list
- __journal_remove_checkpoint
- __journal_insert_checkpoint
- __journal_drop_transaction
/*
* linux/fs/jbd/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 checkpoint list.
*
* Called with j_list_lock held.
*/
static inline void __buffer_unlink_first(struct journal_head *jh)
{
transaction_t *transaction = jh->b_cp_transaction;
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;
}
}
/*
* Unlink a buffer from a transaction checkpoint(io) list.
*
* Called with j_list_lock held.
*/
static inline void __buffer_unlink(struct journal_head *jh)
{
transaction_t *transaction = jh->b_cp_transaction;
__buffer_unlink_first(jh);
if (transaction->t_checkpoint_io_list == jh) {
transaction->t_checkpoint_io_list = jh->b_cpnext;
if (transaction->t_checkpoint_io_list == jh)
transaction->t_checkpoint_io_list = NULL;
}
}
/*
* Move a buffer from the checkpoint list to the checkpoint io list
*
* Called with j_list_lock held
*/
static inline void __buffer_relink_io(struct journal_head *jh)
{
transaction_t *transaction = jh->b_cp_transaction;
__buffer_unlink_first(jh);
if (!transaction->t_checkpoint_io_list) {
jh->b_cpnext = jh->b_cpprev = jh;
} else {
jh->b_cpnext = transaction->t_checkpoint_io_list;
jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
jh->b_cpprev->b_cpnext = jh;
jh->b_cpnext->b_cpprev = jh;
}
transaction->t_checkpoint_io_list = jh;
}
/*
* Try to release a checkpointed buffer from its transaction.
* Returns 1 if we released it and 2 if we also released the
* whole transaction.
*
* 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");
ret = __journal_remove_checkpoint(jh) + 1;
jbd_unlock_bh_state(bh);
journal_remove_journal_head(bh);
BUFFER_TRACE(bh, "release");
__brelse(bh);
} 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);
mutex_lock(&journal->j_checkpoint_mutex);
/*
* 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);
}
mutex_unlock(&journal->j_checkpoint_mutex);
}
}
/*
* 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)
__releases(journal->j_list_lock)
{
get_bh(bh);
spin_unlock(&journal->j_list_lock);
jbd_lock_bh_state(bh);
jbd_unlock_bh_state(bh);
put_bh(bh);
}
/*
* Clean up transaction's list of buffers submitted for io.
* We wait for any pending IO to complete and remove any clean
* buffers. Note that we take the buffers in the opposite ordering
* from the one in which they were submitted for IO.
*
* Called with j_list_lock held.
*/
static void __wait_cp_io(journal_t *journal, transaction_t *transaction)
{
struct journal_head *jh;
struct buffer_head *bh;
tid_t this_tid;
int released = 0;
this_tid = transaction->t_tid;
restart:
/* Did somebody clean up the transaction in the meanwhile? */
if (journal->j_checkpoint_transactions != transaction ||
transaction->t_tid != this_tid)
return;
while (!released && transaction->t_checkpoint_io_list) {
jh = transaction->t_checkpoint_io_list;
bh = jh2bh(jh);
if (!jbd_trylock_bh_state(bh)) {
jbd_sync_bh(journal, bh);
spin_lock(&journal->j_list_lock);
goto restart;
}
if (buffer_locked(bh)) {
atomic_inc(&bh->b_count);
spin_unlock(&journal->j_list_lock);
jbd_unlock_bh_state(bh);
wait_on_buffer(bh);
/* the journal_head may have gone by now */
BUFFER_TRACE(bh, "brelse");
__brelse(bh);
spin_lock(&journal->j_list_lock);
goto restart;
}
/*
* Now in whatever state the buffer currently is, we know that
* it has been written out and so we can drop it from the list
*/
released = __journal_remove_checkpoint(jh);
jbd_unlock_bh_state(bh);
journal_remove_journal_head(bh);
__brelse(bh);
}
}
#define NR_BATCH 64
static void
__flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
{
int i;
ll_rw_block(SWRITE, *batch_count, bhs);
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 and drops it if 1 is returned
* Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
*/
static int __process_buffer(journal_t *journal, struct journal_head *jh,
struct buffer_head **bhs, int *batch_count)
{
struct buffer_head *bh = jh2bh(jh);
int ret = 0;
if (buffer_locked(bh)) {
atomic_inc(&bh->b_count);
spin_unlock(&journal->j_list_lock);
jbd_unlock_bh_state(bh);
wait_on_buffer(bh);
/* the journal_head may have gone by now */
BUFFER_TRACE(bh, "brelse");
__brelse(bh);
ret = 1;
} else 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);
ret = 1;
} else if (!buffer_dirty(bh)) {
J_ASSERT_JH(jh, !buffer_jbddirty(bh));
BUFFER_TRACE(bh, "remove from checkpoint");
__journal_remove_checkpoint(jh);
spin_unlock(&journal->j_list_lock);
jbd_unlock_bh_state(bh);
journal_remove_journal_head(bh);
__brelse(bh);
ret = 1;
} else {
/*
* 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;
__buffer_relink_io(jh);
jbd_unlock_bh_state(bh);
(*batch_count)++;
if (*batch_count == NR_BATCH) {
spin_unlock(&journal->j_list_lock);
__flush_batch(journal, bhs, batch_count);
ret = 1;
}
}
return ret;
}
/*
* Perform an actual checkpoint. We take the first transaction on the
* list of transactions to be checkpointed and send all its buffers
* to disk. We submit larger chunks of data at once.
*
* The journal should be locked before calling this function.
*/
int log_do_checkpoint(journal_t *journal)
{
transaction_t *transaction;
tid_t this_tid;
int result;
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. Take one transaction
* and write it.
*/
spin_lock(&journal->j_list_lock);
if (!journal->j_checkpoint_transactions)
goto out;
transaction = journal->j_checkpoint_transactions;
this_tid = transaction->t_tid;
restart:
/*
* If someone cleaned up this transaction while we slept, we're
* done (maybe it's a new transaction, but it fell at the same
* address).
*/
if (journal->j_checkpoint_transactions == transaction &&
transaction->t_tid == this_tid) {
int batch_count = 0;
struct buffer_head *bhs[NR_BATCH];
struct journal_head *jh;
int retry = 0;
while (!retry && transaction->t_checkpoint_list) {
struct buffer_head *bh;
jh = transaction->t_checkpoint_list;
bh = jh2bh(jh);
if (!jbd_trylock_bh_state(bh)) {
jbd_sync_bh(journal, bh);
retry = 1;
break;
}
retry = __process_buffer(journal, jh, bhs,&batch_count);
if (!retry && (need_resched() ||
spin_needbreak(&journal->j_list_lock))) {
spin_unlock(&journal->j_list_lock);
retry = 1;
break;
}
}
if (batch_count) {
if (!retry) {
spin_unlock(&journal->j_list_lock);
retry = 1;
}
__flush_batch(journal, bhs, &batch_count);
}
if (retry) {
spin_lock(&journal->j_list_lock);
goto restart;
}
/*
* Now we have cleaned up the first transaction's checkpoint
* list. Let's clean up the second one
*/
__wait_cp_io(journal, transaction);
}
out:
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_one_cp_list
*
* Find all the written-back checkpoint buffers in the given list and release them.
*
* Called with the journal locked.
* Called with j_list_lock held.
* Returns number of bufers reaped (for debug)
*/
static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
{
struct journal_head *last_jh;
struct journal_head *next_jh = jh;
int ret, freed = 0;
*released = 0;
if (!jh)
return 0;
last_jh = jh->b_cpprev;
do {
jh = next_jh;
next_jh = jh->b_cpnext;
/* Use trylock because of the ranking */
if (jbd_trylock_bh_state(jh2bh(jh))) {
ret = __try_to_free_cp_buf(jh);
if (ret) {
freed++;
if (ret == 2) {
*released = 1;
return freed;
}
}
}
/*
* 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())
return freed;
} while (jh != last_jh);
return freed;
}
/*
* 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 buffers reaped (for debug)
*/
int __journal_clean_checkpoint_list(journal_t *journal)
{
transaction_t *transaction, *last_transaction, *next_transaction;
int ret = 0;
int released;
transaction = journal->j_checkpoint_transactions;
if (!transaction)
goto out;
last_transaction = transaction->t_cpprev;
next_transaction = transaction;
do {
transaction = next_transaction;
next_transaction = transaction->t_cpnext;
ret += journal_clean_one_cp_list(transaction->
t_checkpoint_list, &released);
/*
* 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;
if (released)
continue;
/*
* It is essential that we are as careful as in the case of
* t_checkpoint_list with removing the buffer from the list as
* we can possibly see not yet submitted buffers on io_list
*/
ret += journal_clean_one_cp_list(transaction->
t_checkpoint_io_list, &released);
if (need_resched())
goto out;
} 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
* lists until they have been rewritten, at which point this function is
* called to remove the buffer from the existing transaction's
* checkpoint lists.
*
* The function returns 1 if it frees the transaction, 0 otherwise.
*
* This function is called with the journal locked.
* This function is called with j_list_lock held.
* This function is called with jbd_lock_bh_state(jh2bh(jh))
*/
int __journal_remove_checkpoint(struct journal_head *jh)
{
transaction_t *transaction;
journal_t *journal;
int ret = 0;
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);
jh->b_cp_transaction = NULL;
if (transaction->t_checkpoint_list != NULL ||
transaction->t_checkpoint_io_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 running or committing transaction's checkpoing list,
* then even if the checkpoint list is empty, the transaction obviously
* cannot be dropped!
*
* The locking here around t_state is a bit sleazy.
* See the comment at the end of journal_commit_transaction().
*/
if (transaction->t_state != T_FINISHED) {
JBUFFER_TRACE(jh, "belongs to running/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);
ret = 1;
out:
JBUFFER_TRACE(jh, "exit");
return ret;
}
/*
* 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_checkpoint_io_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);
}