diff options
Diffstat (limited to 'fs/jbd2/checkpoint.c')
| -rw-r--r-- | fs/jbd2/checkpoint.c | 729 |
1 files changed, 729 insertions, 0 deletions
diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c new file mode 100644 index 000000000..f033ac807 --- /dev/null +++ b/fs/jbd2/checkpoint.c @@ -0,0 +1,729 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * linux/fs/jbd2/checkpoint.c + * + * Written by Stephen C. Tweedie <sct@redhat.com>, 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; + } +} + +/* + * Check a checkpoint buffer could be release or not. + * + * Requires j_list_lock + */ +static inline bool __cp_buffer_busy(struct journal_head *jh) +{ + struct buffer_head *bh = jh2bh(jh); + + return (jh->b_transaction || buffer_locked(bh) || buffer_dirty(bh)); +} + +/* + * __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; + + if (journal->j_committing_transaction) + tid = journal->j_committing_transaction->t_tid; + 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; yay! */ + ; + } else if (tid) { + /* + * 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; + +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_tid) + first_tid = transaction->t_tid; + 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 && next_tid) + 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); +} |