linux/fs/jbd2/checkpoint.c

// 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)
{ … }

/*
 * __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)
{ … }

static void
__flush_batch(journal_t *journal, int *batch_count)
{ … }

/*
 * 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)
{ … }

/*
 * 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)
{ … }


/* 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)
{ … }

/*
 * 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)
{ … }

/*
 * 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)
{ … }

/*
 * 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)
{ … }

/*
 * 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)
{ … }

/*
 * 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)
{ … }

/*
 * 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)
{ … }

/*
 * 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)
{ … }