// SPDX-License-Identifier: GPL-2.0+
/*
* linux/fs/jbd2/checkpoint.c
*
* Written by Stephen C. Tweedie <[email protected]>, 1999
*
* Copyright 1999 Red Hat Software --- All Rights Reserved
*
* 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/jbd2.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <trace/events/jbd2.h>
/*
* Unlink a buffer from a transaction checkpoint list.
*
* Called with j_list_lock held.
*/
static inline void __buffer_unlink(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;
}
}
/*
* __jbd2_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 __jbd2_log_wait_for_space(journal_t *journal)
__acquires(&journal->j_state_lock)
__releases(&journal->j_state_lock)
{
int nblocks, space_left;
/* assert_spin_locked(&journal->j_state_lock); */
nblocks = journal->j_max_transaction_buffers;
while (jbd2_log_space_left(journal) < nblocks) {
write_unlock(&journal->j_state_lock);
mutex_lock_io(&journal->j_checkpoint_mutex);
/*
* Test again, another process may have checkpointed while we
* were waiting for the checkpoint lock. If there are no
* transactions ready to be checkpointed, try to recover
* journal space by calling cleanup_journal_tail(), and if
* that doesn't work, by waiting for the currently committing
* transaction to complete. If there is absolutely no way
* to make progress, this is either a BUG or corrupted
* filesystem, so abort the journal and leave a stack
* trace for forensic evidence.
*/
write_lock(&journal->j_state_lock);
if (journal->j_flags & JBD2_ABORT) {
mutex_unlock(&journal->j_checkpoint_mutex);
return;
}
spin_lock(&journal->j_list_lock);
space_left = jbd2_log_space_left(journal);
if (space_left < nblocks) {
int chkpt = journal->j_checkpoint_transactions != NULL;
tid_t tid = 0;
bool has_transaction = false;
if (journal->j_committing_transaction) {
tid = journal->j_committing_transaction->t_tid;
has_transaction = true;
}
spin_unlock(&journal->j_list_lock);
write_unlock(&journal->j_state_lock);
if (chkpt) {
jbd2_log_do_checkpoint(journal);
} else if (jbd2_cleanup_journal_tail(journal) <= 0) {
/*
* We were able to recover space or the
* journal was aborted due to an error.
*/
;
} else if (has_transaction) {
/*
* jbd2_journal_commit_transaction() may want
* to take the checkpoint_mutex if JBD2_FLUSHED
* is set. So we need to temporarily drop it.
*/
mutex_unlock(&journal->j_checkpoint_mutex);
jbd2_log_wait_commit(journal, tid);
write_lock(&journal->j_state_lock);
continue;
} else {
printk(KERN_ERR "%s: needed %d blocks and "
"only had %d space available\n",
__func__, nblocks, space_left);
printk(KERN_ERR "%s: no way to get more "
"journal space in %s\n", __func__,
journal->j_devname);
WARN_ON(1);
jbd2_journal_abort(journal, -EIO);
}
write_lock(&journal->j_state_lock);
} else {
spin_unlock(&journal->j_list_lock);
}
mutex_unlock(&journal->j_checkpoint_mutex);
}
}
static void
__flush_batch(journal_t *journal, int *batch_count)
{
int i;
struct blk_plug plug;
blk_start_plug(&plug);
for (i = 0; i < *batch_count; i++)
write_dirty_buffer(journal->j_chkpt_bhs[i], REQ_SYNC);
blk_finish_plug(&plug);
for (i = 0; i < *batch_count; i++) {
struct buffer_head *bh = journal->j_chkpt_bhs[i];
BUFFER_TRACE(bh, "brelse");
__brelse(bh);
journal->j_chkpt_bhs[i] = NULL;
}
*batch_count = 0;
}
/*
* 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.
* Called with j_checkpoint_mutex held.
*/
int jbd2_log_do_checkpoint(journal_t *journal)
{
struct journal_head *jh;
struct buffer_head *bh;
transaction_t *transaction;
tid_t this_tid;
int result, batch_count = 0;
jbd2_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 = jbd2_cleanup_journal_tail(journal);
trace_jbd2_checkpoint(journal, result);
jbd2_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;
if (transaction->t_chp_stats.cs_chp_time == 0)
transaction->t_chp_stats.cs_chp_time = jiffies;
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)
goto out;
/* checkpoint all of the transaction's buffers */
while (transaction->t_checkpoint_list) {
jh = transaction->t_checkpoint_list;
bh = jh2bh(jh);
if (jh->b_transaction != NULL) {
transaction_t *t = jh->b_transaction;
tid_t tid = t->t_tid;
transaction->t_chp_stats.cs_forced_to_close++;
spin_unlock(&journal->j_list_lock);
if (unlikely(journal->j_flags & JBD2_UNMOUNT))
/*
* The journal thread is dead; so
* starting and waiting for a commit
* to finish will cause us to wait for
* a _very_ long time.
*/
printk(KERN_ERR
"JBD2: %s: Waiting for Godot: block %llu\n",
journal->j_devname, (unsigned long long) bh->b_blocknr);
if (batch_count)
__flush_batch(journal, &batch_count);
jbd2_log_start_commit(journal, tid);
/*
* jbd2_journal_commit_transaction() may want
* to take the checkpoint_mutex if JBD2_FLUSHED
* is set, jbd2_update_log_tail() called by
* jbd2_journal_commit_transaction() may also take
* checkpoint_mutex. So we need to temporarily
* drop it.
*/
mutex_unlock(&journal->j_checkpoint_mutex);
jbd2_log_wait_commit(journal, tid);
mutex_lock_io(&journal->j_checkpoint_mutex);
spin_lock(&journal->j_list_lock);
goto restart;
}
if (!trylock_buffer(bh)) {
/*
* The buffer is locked, it may be writing back, or
* flushing out in the last couple of cycles, or
* re-adding into a new transaction, need to check
* it again until it's unlocked.
*/
get_bh(bh);
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 retry;
} else if (!buffer_dirty(bh)) {
unlock_buffer(bh);
BUFFER_TRACE(bh, "remove from checkpoint");
/*
* If the transaction was released or the checkpoint
* list was empty, we're done.
*/
if (__jbd2_journal_remove_checkpoint(jh) ||
!transaction->t_checkpoint_list)
goto out;
} else {
unlock_buffer(bh);
/*
* We are about to write the buffer, it could be
* raced by some other transaction shrink or buffer
* re-log logic once we release the j_list_lock,
* leave it on the checkpoint list and check status
* again to make sure it's clean.
*/
BUFFER_TRACE(bh, "queue");
get_bh(bh);
J_ASSERT_BH(bh, !buffer_jwrite(bh));
journal->j_chkpt_bhs[batch_count++] = bh;
transaction->t_chp_stats.cs_written++;
transaction->t_checkpoint_list = jh->b_cpnext;
}
if ((batch_count == JBD2_NR_BATCH) ||
need_resched() || spin_needbreak(&journal->j_list_lock) ||
jh2bh(transaction->t_checkpoint_list) == journal->j_chkpt_bhs[0])
goto unlock_and_flush;
}
if (batch_count) {
unlock_and_flush:
spin_unlock(&journal->j_list_lock);
retry:
if (batch_count)
__flush_batch(journal, &batch_count);
spin_lock(&journal->j_list_lock);
goto restart;
}
out:
spin_unlock(&journal->j_list_lock);
result = jbd2_cleanup_journal_tail(journal);
return (result < 0) ? result : 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 super block if
* checkpointing may have failed. Otherwise, we would lose some metadata
* buffers which should be written-back to the filesystem.
*/
int jbd2_cleanup_journal_tail(journal_t *journal)
{
tid_t first_tid;
unsigned long blocknr;
if (is_journal_aborted(journal))
return -EIO;
if (!jbd2_journal_get_log_tail(journal, &first_tid, &blocknr))
return 1;
J_ASSERT(blocknr != 0);
/*
* We need to make sure that any blocks that were recently written out
* --- perhaps by jbd2_log_do_checkpoint() --- are flushed out before
* we drop the transactions from the journal. It's unlikely this will
* be necessary, especially with an appropriately sized journal, but we
* need this to guarantee correctness. Fortunately
* jbd2_cleanup_journal_tail() doesn't get called all that often.
*/
if (journal->j_flags & JBD2_BARRIER)
blkdev_issue_flush(journal->j_fs_dev);
return __jbd2_update_log_tail(journal, first_tid, blocknr);
}
/* Checkpoint list management */
/*
* journal_shrink_one_cp_list
*
* Find all the written-back checkpoint buffers in the given list
* and try to release them. If the whole transaction is released, set
* the 'released' parameter. Return the number of released checkpointed
* buffers.
*
* Called with j_list_lock held.
*/
static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
enum jbd2_shrink_type type,
bool *released)
{
struct journal_head *last_jh;
struct journal_head *next_jh = jh;
unsigned long nr_freed = 0;
int ret;
*released = false;
if (!jh)
return 0;
last_jh = jh->b_cpprev;
do {
jh = next_jh;
next_jh = jh->b_cpnext;
if (type == JBD2_SHRINK_DESTROY) {
ret = __jbd2_journal_remove_checkpoint(jh);
} else {
ret = jbd2_journal_try_remove_checkpoint(jh);
if (ret < 0) {
if (type == JBD2_SHRINK_BUSY_SKIP)
continue;
break;
}
}
nr_freed++;
if (ret) {
*released = true;
break;
}
if (need_resched())
break;
} while (jh != last_jh);
return nr_freed;
}
/*
* jbd2_journal_shrink_checkpoint_list
*
* Find 'nr_to_scan' written-back checkpoint buffers in the journal
* and try to release them. Return the number of released checkpointed
* buffers.
*
* Called with j_list_lock held.
*/
unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
unsigned long *nr_to_scan)
{
transaction_t *transaction, *last_transaction, *next_transaction;
bool __maybe_unused released;
tid_t first_tid = 0, last_tid = 0, next_tid = 0;
tid_t tid = 0;
unsigned long nr_freed = 0;
unsigned long freed;
bool first_set = false;
again:
spin_lock(&journal->j_list_lock);
if (!journal->j_checkpoint_transactions) {
spin_unlock(&journal->j_list_lock);
goto out;
}
/*
* Get next shrink transaction, resume previous scan or start
* over again. If some others do checkpoint and drop transaction
* from the checkpoint list, we ignore saved j_shrink_transaction
* and start over unconditionally.
*/
if (journal->j_shrink_transaction)
transaction = journal->j_shrink_transaction;
else
transaction = journal->j_checkpoint_transactions;
if (!first_set) {
first_tid = transaction->t_tid;
first_set = true;
}
last_transaction = journal->j_checkpoint_transactions->t_cpprev;
next_transaction = transaction;
last_tid = last_transaction->t_tid;
do {
transaction = next_transaction;
next_transaction = transaction->t_cpnext;
tid = transaction->t_tid;
freed = journal_shrink_one_cp_list(transaction->t_checkpoint_list,
JBD2_SHRINK_BUSY_SKIP, &released);
nr_freed += freed;
(*nr_to_scan) -= min(*nr_to_scan, freed);
if (*nr_to_scan == 0)
break;
if (need_resched() || spin_needbreak(&journal->j_list_lock))
break;
} while (transaction != last_transaction);
if (transaction != last_transaction) {
journal->j_shrink_transaction = next_transaction;
next_tid = next_transaction->t_tid;
} else {
journal->j_shrink_transaction = NULL;
next_tid = 0;
}
spin_unlock(&journal->j_list_lock);
cond_resched();
if (*nr_to_scan && journal->j_shrink_transaction)
goto again;
out:
trace_jbd2_shrink_checkpoint_list(journal, first_tid, tid, last_tid,
nr_freed, next_tid);
return nr_freed;
}
/*
* journal_clean_checkpoint_list
*
* Find all the written-back checkpoint buffers in the journal and release them.
* If 'type' is JBD2_SHRINK_DESTROY, release all buffers unconditionally. If
* 'type' is JBD2_SHRINK_BUSY_STOP, will stop release buffers if encounters a
* busy buffer. To avoid wasting CPU cycles scanning the buffer list in some
* cases, don't pass JBD2_SHRINK_BUSY_SKIP 'type' for this function.
*
* Called with j_list_lock held.
*/
void __jbd2_journal_clean_checkpoint_list(journal_t *journal,
enum jbd2_shrink_type type)
{
transaction_t *transaction, *last_transaction, *next_transaction;
bool released;
WARN_ON_ONCE(type == JBD2_SHRINK_BUSY_SKIP);
transaction = journal->j_checkpoint_transactions;
if (!transaction)
return;
last_transaction = transaction->t_cpprev;
next_transaction = transaction;
do {
transaction = next_transaction;
next_transaction = transaction->t_cpnext;
journal_shrink_one_cp_list(transaction->t_checkpoint_list,
type, &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())
return;
/*
* Stop scanning if we couldn't free the transaction. This
* avoids pointless scanning of transactions which still
* weren't checkpointed.
*/
if (!released)
return;
} while (transaction != last_transaction);
}
/*
* Remove buffers from all checkpoint lists as journal is aborted and we just
* need to free memory
*/
void jbd2_journal_destroy_checkpoint(journal_t *journal)
{
/*
* We loop because __jbd2_journal_clean_checkpoint_list() may abort
* early due to a need of rescheduling.
*/
while (1) {
spin_lock(&journal->j_list_lock);
if (!journal->j_checkpoint_transactions) {
spin_unlock(&journal->j_list_lock);
break;
}
__jbd2_journal_clean_checkpoint_list(journal, JBD2_SHRINK_DESTROY);
spin_unlock(&journal->j_list_lock);
cond_resched();
}
}
/*
* 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.
* The function can free jh and bh.
*
* This function is called with j_list_lock held.
*/
int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
{
struct transaction_chp_stats_s *stats;
transaction_t *transaction;
journal_t *journal;
JBUFFER_TRACE(jh, "entry");
transaction = jh->b_cp_transaction;
if (!transaction) {
JBUFFER_TRACE(jh, "not on transaction");
return 0;
}
journal = transaction->t_journal;
JBUFFER_TRACE(jh, "removing from transaction");
__buffer_unlink(jh);
jh->b_cp_transaction = NULL;
percpu_counter_dec(&journal->j_checkpoint_jh_count);
jbd2_journal_put_journal_head(jh);
/* Is this transaction empty? */
if (transaction->t_checkpoint_list)
return 0;
/*
* 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 jbd2_journal_commit_transaction().
*/
if (transaction->t_state != T_FINISHED)
return 0;
/*
* OK, that was the last buffer for the transaction, we can now
* safely remove this transaction from the log.
*/
stats = &transaction->t_chp_stats;
if (stats->cs_chp_time)
stats->cs_chp_time = jbd2_time_diff(stats->cs_chp_time,
jiffies);
trace_jbd2_checkpoint_stats(journal->j_fs_dev->bd_dev,
transaction->t_tid, stats);
__jbd2_journal_drop_transaction(journal, transaction);
jbd2_journal_free_transaction(transaction);
return 1;
}
/*
* Check the checkpoint buffer and try to remove it from the checkpoint
* list if it's clean. Returns -EBUSY if it is not clean, returns 1 if
* it frees the transaction, 0 otherwise.
*
* This function is called with j_list_lock held.
*/
int jbd2_journal_try_remove_checkpoint(struct journal_head *jh)
{
struct buffer_head *bh = jh2bh(jh);
if (jh->b_transaction)
return -EBUSY;
if (!trylock_buffer(bh))
return -EBUSY;
if (buffer_dirty(bh)) {
unlock_buffer(bh);
return -EBUSY;
}
unlock_buffer(bh);
/*
* Buffer is clean and the IO has finished (we held the buffer
* lock) so the checkpoint is done. We can safely remove the
* buffer from this transaction.
*/
JBUFFER_TRACE(jh, "remove from checkpoint list");
return __jbd2_journal_remove_checkpoint(jh);
}
/*
* 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 __jbd2_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);
/* Get reference for checkpointing transaction */
jbd2_journal_grab_journal_head(jh2bh(jh));
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;
percpu_counter_inc(&transaction->t_journal->j_checkpoint_jh_count);
}
/*
* 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 __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
{
assert_spin_locked(&journal->j_list_lock);
journal->j_shrink_transaction = NULL;
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_forget == NULL);
J_ASSERT(transaction->t_shadow_list == NULL);
J_ASSERT(transaction->t_checkpoint_list == NULL);
J_ASSERT(atomic_read(&transaction->t_updates) == 0);
J_ASSERT(journal->j_committing_transaction != transaction);
J_ASSERT(journal->j_running_transaction != transaction);
trace_jbd2_drop_transaction(journal, transaction);
jbd2_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
}
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