diff options
Diffstat (limited to 'fs/jbd2/checkpoint.c')
| -rw-r--r-- | fs/jbd2/checkpoint.c | 644 |
1 files changed, 644 insertions, 0 deletions
diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c new file mode 100644 index 000000000..4227dc4f7 --- /dev/null +++ b/fs/jbd2/checkpoint.c @@ -0,0 +1,644 @@ +/* + * linux/fs/jbd2/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/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_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 + */ +static int __try_to_free_cp_buf(struct journal_head *jh) +{ + int ret = 0; + struct buffer_head *bh = jh2bh(jh); + + if (jh->b_transaction == NULL && !buffer_locked(bh) && + !buffer_dirty(bh) && !buffer_write_io_error(bh)) { + JBUFFER_TRACE(jh, "remove from checkpoint list"); + ret = __jbd2_journal_remove_checkpoint(jh) + 1; + } + return ret; +} + +/* + * __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) +{ + int nblocks, space_left; + /* assert_spin_locked(&journal->j_state_lock); */ + + nblocks = jbd2_space_needed(journal); + while (jbd2_log_space_left(journal) < nblocks) { + write_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. 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); + nblocks = jbd2_space_needed(journal); + 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, 0); + } + 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], WRITE_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); + } + *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; + + 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 = jbd2_cleanup_journal_tail(journal); + trace_jbd2_checkpoint(journal, result); + 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. + */ + result = 0; + 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 (buffer_locked(bh)) { + spin_unlock(&journal->j_list_lock); + get_bh(bh); + wait_on_buffer(bh); + /* the journal_head may have gone by now */ + BUFFER_TRACE(bh, "brelse"); + __brelse(bh); + goto retry; + } + 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); + + jbd2_log_start_commit(journal, tid); + jbd2_log_wait_commit(journal, tid); + goto retry; + } + if (!buffer_dirty(bh)) { + if (unlikely(buffer_write_io_error(bh)) && !result) + result = -EIO; + BUFFER_TRACE(bh, "remove from checkpoint"); + if (__jbd2_journal_remove_checkpoint(jh)) + /* The transaction was released; we're done */ + goto out; + continue; + } + /* + * 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)); + journal->j_chkpt_bhs[batch_count++] = bh; + __buffer_relink_io(jh); + transaction->t_chp_stats.cs_written++; + if ((batch_count == JBD2_NR_BATCH) || + need_resched() || + spin_needbreak(&journal->j_list_lock)) + 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; + } + + /* + * Now we issued all of the transaction's buffers, let's deal + * with the buffers that are out for I/O. + */ +restart2: + /* Did somebody clean up the transaction in the meanwhile? */ + if (journal->j_checkpoint_transactions != transaction || + transaction->t_tid != this_tid) + goto out; + + while (transaction->t_checkpoint_io_list) { + jh = transaction->t_checkpoint_io_list; + bh = jh2bh(jh); + if (buffer_locked(bh)) { + spin_unlock(&journal->j_list_lock); + get_bh(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 restart2; + } + if (unlikely(buffer_write_io_error(bh)) && !result) + result = -EIO; + + /* + * 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 + */ + if (__jbd2_journal_remove_checkpoint(jh)) + break; + } +out: + spin_unlock(&journal->j_list_lock); + if (result < 0) + jbd2_journal_abort(journal, result); + else + 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, GFP_NOFS, NULL); + + return __jbd2_update_log_tail(journal, first_tid, blocknr); +} + + +/* Checkpoint list management */ + +/* + * journal_clean_one_cp_list + * + * Find all the written-back checkpoint buffers in the given list and + * release them. + * + * Called with j_list_lock held. + * Returns 1 if we freed the transaction, 0 otherwise. + */ +static int journal_clean_one_cp_list(struct journal_head *jh) +{ + struct journal_head *last_jh; + struct journal_head *next_jh = jh; + int ret; + int freed = 0; + + if (!jh) + return 0; + + last_jh = jh->b_cpprev; + do { + jh = next_jh; + next_jh = jh->b_cpnext; + ret = __try_to_free_cp_buf(jh); + if (!ret) + return freed; + if (ret == 2) + return 1; + freed = 1; + /* + * 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 j_list_lock held. + */ +void __jbd2_journal_clean_checkpoint_list(journal_t *journal) +{ + transaction_t *transaction, *last_transaction, *next_transaction; + int ret; + + 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; + ret = journal_clean_one_cp_list(transaction->t_checkpoint_list); + /* + * 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; + if (ret) + 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); + 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 (!ret) + return; + } while (transaction != last_transaction); +} + +/* + * 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; + 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; + + JBUFFER_TRACE(jh, "removing from transaction"); + __buffer_unlink(jh); + jh->b_cp_transaction = NULL; + jbd2_journal_put_journal_head(jh); + + if (transaction->t_checkpoint_list != NULL || + transaction->t_checkpoint_io_list != NULL) + goto out; + + /* + * 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) + goto out; + + /* 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); + ret = 1; +out: + 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 __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; +} + +/* + * 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); + 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(transaction->t_checkpoint_io_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); + + jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid); +} |