// SPDX-License-Identifier: GPL-2.0+ /* * linux/fs/jbd2/checkpoint.c * * Written by Stephen C. Tweedie , 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 #include #include #include #include #include #include /* * 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 */ enum shrink_type {SHRINK_DESTROY, SHRINK_BUSY_STOP, SHRINK_BUSY_SKIP}; /* * 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 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 == SHRINK_DESTROY) { ret = __jbd2_journal_remove_checkpoint(jh); } else { ret = jbd2_journal_try_remove_checkpoint(jh); if (ret < 0) { if (type == 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, 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 'destroy' is set, release all buffers unconditionally. * * Called with j_list_lock held. */ void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy) { transaction_t *transaction, *last_transaction, *next_transaction; enum shrink_type type; bool released; transaction = journal->j_checkpoint_transactions; if (!transaction) return; type = destroy ? SHRINK_DESTROY : SHRINK_BUSY_STOP; 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, true); 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; struct buffer_head *bh = jh2bh(jh); 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"); /* * If we have failed to write the buffer out to disk, the filesystem * may become inconsistent. We cannot abort the journal here since * we hold j_list_lock and we have to be careful about races with * jbd2_journal_destroy(). So mark the writeback IO error in the * journal here and we abort the journal later from a better context. */ if (buffer_write_io_error(bh)) set_bit(JBD2_CHECKPOINT_IO_ERROR, &journal->j_atomic_flags); __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); }