/* * linux/fs/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/jbd.h> #include <linux/errno.h> #include <linux/slab.h> /* * Unlink a buffer from a transaction. * * Called with j_list_lock held. */ static inline void __buffer_unlink(struct journal_head *jh) { transaction_t *transaction; transaction = jh->b_cp_transaction; jh->b_cp_transaction = NULL; 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; } /* * Try to release a checkpointed buffer from its transaction. * Returns 1 if we released it. * Requires j_list_lock * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it */ static int __try_to_free_cp_buf(struct journal_head *jh) { int ret = 0; struct buffer_head *bh = jh2bh(jh); if (jh->b_jlist == BJ_None && !buffer_locked(bh) && !buffer_dirty(bh)) { JBUFFER_TRACE(jh, "remove from checkpoint list"); __journal_remove_checkpoint(jh); jbd_unlock_bh_state(bh); journal_remove_journal_head(bh); BUFFER_TRACE(bh, "release"); __brelse(bh); ret = 1; } else { jbd_unlock_bh_state(bh); } return ret; } /* * __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 __log_wait_for_space(journal_t *journal) { int nblocks; assert_spin_locked(&journal->j_state_lock); nblocks = jbd_space_needed(journal); while (__log_space_left(journal) < nblocks) { if (journal->j_flags & JFS_ABORT) return; spin_unlock(&journal->j_state_lock); down(&journal->j_checkpoint_sem); /* * Test again, another process may have checkpointed while we * were waiting for the checkpoint lock */ spin_lock(&journal->j_state_lock); nblocks = jbd_space_needed(journal); if (__log_space_left(journal) < nblocks) { spin_unlock(&journal->j_state_lock); log_do_checkpoint(journal); spin_lock(&journal->j_state_lock); } up(&journal->j_checkpoint_sem); } } /* * We were unable to perform jbd_trylock_bh_state() inside j_list_lock. * The caller must restart a list walk. Wait for someone else to run * jbd_unlock_bh_state(). */ static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh) { get_bh(bh); spin_unlock(&journal->j_list_lock); jbd_lock_bh_state(bh); jbd_unlock_bh_state(bh); put_bh(bh); } /* * Clean up a transaction's checkpoint list. * * We wait for any pending IO to complete and make sure any clean * buffers are removed from the transaction. * * Return 1 if we performed any actions which might have destroyed the * checkpoint. (journal_remove_checkpoint() deletes the transaction when * the last checkpoint buffer is cleansed) * * Called with j_list_lock held. */ static int __cleanup_transaction(journal_t *journal, transaction_t *transaction) { struct journal_head *jh, *next_jh, *last_jh; struct buffer_head *bh; int ret = 0; assert_spin_locked(&journal->j_list_lock); jh = transaction->t_checkpoint_list; if (!jh) return 0; last_jh = jh->b_cpprev; next_jh = jh; do { jh = next_jh; bh = jh2bh(jh); if (buffer_locked(bh)) { atomic_inc(&bh->b_count); 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 out_return_1; } /* * This is foul */ if (!jbd_trylock_bh_state(bh)) { jbd_sync_bh(journal, bh); goto out_return_1; } if (jh->b_transaction != NULL) { transaction_t *t = jh->b_transaction; tid_t tid = t->t_tid; spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); log_start_commit(journal, tid); log_wait_commit(journal, tid); goto out_return_1; } /* * AKPM: I think the buffer_jbddirty test is redundant - it * shouldn't have NULL b_transaction? */ next_jh = jh->b_cpnext; if (!buffer_dirty(bh) && !buffer_jbddirty(bh)) { BUFFER_TRACE(bh, "remove from checkpoint"); __journal_remove_checkpoint(jh); jbd_unlock_bh_state(bh); journal_remove_journal_head(bh); __brelse(bh); ret = 1; } else { jbd_unlock_bh_state(bh); } } while (jh != last_jh); return ret; out_return_1: spin_lock(&journal->j_list_lock); return 1; } #define NR_BATCH 64 static void __flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count) { int i; spin_unlock(&journal->j_list_lock); ll_rw_block(SWRITE, *batch_count, bhs); spin_lock(&journal->j_list_lock); for (i = 0; i < *batch_count; i++) { struct buffer_head *bh = bhs[i]; clear_buffer_jwrite(bh); BUFFER_TRACE(bh, "brelse"); __brelse(bh); } *batch_count = 0; } /* * Try to flush one buffer from the checkpoint list to disk. * * Return 1 if something happened which requires us to abort the current * scan of the checkpoint list. * * Called with j_list_lock held. * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it */ static int __flush_buffer(journal_t *journal, struct journal_head *jh, struct buffer_head **bhs, int *batch_count, int *drop_count) { struct buffer_head *bh = jh2bh(jh); int ret = 0; if (buffer_dirty(bh) && !buffer_locked(bh) && jh->b_jlist == BJ_None) { J_ASSERT_JH(jh, jh->b_transaction == NULL); /* * 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)); set_buffer_jwrite(bh); bhs[*batch_count] = bh; jbd_unlock_bh_state(bh); (*batch_count)++; if (*batch_count == NR_BATCH) { __flush_batch(journal, bhs, batch_count); ret = 1; } } else { int last_buffer = 0; if (jh->b_cpnext == jh) { /* We may be about to drop the transaction. Tell the * caller that the lists have changed. */ last_buffer = 1; } if (__try_to_free_cp_buf(jh)) { (*drop_count)++; ret = last_buffer; } } return ret; } /* * Perform an actual checkpoint. We don't write out only enough to * satisfy the current blocked requests: rather we submit a reasonably * sized chunk of the outstanding data to disk at once for * efficiency. __log_wait_for_space() will retry if we didn't free enough. * * However, we _do_ take into account the amount requested so that once * the IO has been queued, we can return as soon as enough of it has * completed to disk. * * The journal should be locked before calling this function. */ int log_do_checkpoint(journal_t *journal) { int result; int batch_count = 0; struct buffer_head *bhs[NR_BATCH]; 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 = cleanup_journal_tail(journal); jbd_debug(1, "cleanup_journal_tail returned %d\n", result); if (result <= 0) return result; /* * OK, we need to start writing disk blocks. Try to free up a * quarter of the log in a single checkpoint if we can. */ /* * AKPM: check this code. I had a feeling a while back that it * degenerates into a busy loop at unmount time. */ spin_lock(&journal->j_list_lock); while (journal->j_checkpoint_transactions) { transaction_t *transaction; struct journal_head *jh, *last_jh, *next_jh; int drop_count = 0; int cleanup_ret, retry = 0; tid_t this_tid; transaction = journal->j_checkpoint_transactions; this_tid = transaction->t_tid; jh = transaction->t_checkpoint_list; last_jh = jh->b_cpprev; next_jh = jh; do { struct buffer_head *bh; jh = next_jh; next_jh = jh->b_cpnext; bh = jh2bh(jh); if (!jbd_trylock_bh_state(bh)) { jbd_sync_bh(journal, bh); spin_lock(&journal->j_list_lock); retry = 1; break; } retry = __flush_buffer(journal, jh, bhs, &batch_count, &drop_count); if (cond_resched_lock(&journal->j_list_lock)) { retry = 1; break; } } while (jh != last_jh && !retry); if (batch_count) { __flush_batch(journal, bhs, &batch_count); retry = 1; } /* * If someone cleaned up this transaction while we slept, we're * done */ if (journal->j_checkpoint_transactions != transaction) break; if (retry) continue; /* * Maybe it's a new transaction, but it fell at the same * address */ if (transaction->t_tid != this_tid) continue; /* * We have walked the whole transaction list without * finding anything to write to disk. We had better be * able to make some progress or we are in trouble. */ cleanup_ret = __cleanup_transaction(journal, transaction); J_ASSERT(drop_count != 0 || cleanup_ret != 0); if (journal->j_checkpoint_transactions != transaction) break; } spin_unlock(&journal->j_list_lock); result = cleanup_journal_tail(journal); if (result < 0) return result; return 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 journal superblock if * we have an abort error outstanding. */ int cleanup_journal_tail(journal_t *journal) { transaction_t * transaction; tid_t first_tid; unsigned long blocknr, freed; /* OK, work out the oldest transaction remaining in the log, and * the log block it starts at. * * If the log is now empty, we need to work out which is the * next transaction ID we will write, and where it will * start. */ spin_lock(&journal->j_state_lock); spin_lock(&journal->j_list_lock); transaction = journal->j_checkpoint_transactions; if (transaction) { first_tid = transaction->t_tid; blocknr = transaction->t_log_start; } else if ((transaction = journal->j_committing_transaction) != NULL) { first_tid = transaction->t_tid; blocknr = transaction->t_log_start; } else if ((transaction = journal->j_running_transaction) != NULL) { first_tid = transaction->t_tid; blocknr = journal->j_head; } else { first_tid = journal->j_transaction_sequence; blocknr = journal->j_head; } spin_unlock(&journal->j_list_lock); J_ASSERT(blocknr != 0); /* If the oldest pinned transaction is at the tail of the log already then there's not much we can do right now. */ if (journal->j_tail_sequence == first_tid) { spin_unlock(&journal->j_state_lock); return 1; } /* OK, update the superblock to recover the freed space. * Physical blocks come first: have we wrapped beyond the end of * the log? */ freed = blocknr - journal->j_tail; if (blocknr < journal->j_tail) freed = freed + journal->j_last - journal->j_first; jbd_debug(1, "Cleaning journal tail from %d to %d (offset %lu), " "freeing %lu\n", journal->j_tail_sequence, first_tid, blocknr, freed); journal->j_free += freed; journal->j_tail_sequence = first_tid; journal->j_tail = blocknr; spin_unlock(&journal->j_state_lock); if (!(journal->j_flags & JFS_ABORT)) journal_update_superblock(journal, 1); return 0; } /* Checkpoint list management */ /* * journal_clean_checkpoint_list * * Find all the written-back checkpoint buffers in the journal and release them. * * Called with the journal locked. * Called with j_list_lock held. * Returns number of bufers reaped (for debug) */ int __journal_clean_checkpoint_list(journal_t *journal) { transaction_t *transaction, *last_transaction, *next_transaction; int ret = 0; transaction = journal->j_checkpoint_transactions; if (transaction == 0) goto out; last_transaction = transaction->t_cpprev; next_transaction = transaction; do { struct journal_head *jh; transaction = next_transaction; next_transaction = transaction->t_cpnext; jh = transaction->t_checkpoint_list; if (jh) { struct journal_head *last_jh = jh->b_cpprev; struct journal_head *next_jh = jh; do { jh = next_jh; next_jh = jh->b_cpnext; /* Use trylock because of the ranknig */ if (jbd_trylock_bh_state(jh2bh(jh))) ret += __try_to_free_cp_buf(jh); /* * 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()) goto out; } while (jh != last_jh); } } while (transaction != last_transaction); out: return ret; } /* * 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 * list until they have been rewritten, at which point this function is * called to remove the buffer from the existing transaction's * checkpoint list. * * This function is called with the journal locked. * This function is called with j_list_lock held. */ void __journal_remove_checkpoint(struct journal_head *jh) { transaction_t *transaction; journal_t *journal; JBUFFER_TRACE(jh, "entry"); if ((transaction = jh->b_cp_transaction) == NULL) { JBUFFER_TRACE(jh, "not on transaction"); goto out; } journal = transaction->t_journal; __buffer_unlink(jh); if (transaction->t_checkpoint_list != NULL) goto out; JBUFFER_TRACE(jh, "transaction has no more buffers"); /* * There is one special case to worry about: if we have just pulled the * buffer off a committing transaction's forget list, then even if the * checkpoint list is empty, the transaction obviously cannot be * dropped! * * The locking here around j_committing_transaction is a bit sleazy. * See the comment at the end of journal_commit_transaction(). */ if (transaction == journal->j_committing_transaction) { JBUFFER_TRACE(jh, "belongs to committing transaction"); goto out; } /* OK, that was the last buffer for the transaction: we can now safely remove this transaction from the log */ __journal_drop_transaction(journal, transaction); /* Just in case anybody was waiting for more transactions to be checkpointed... */ wake_up(&journal->j_wait_logspace); out: JBUFFER_TRACE(jh, "exit"); } /* * 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 __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); 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 __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_sync_datalist == NULL); J_ASSERT(transaction->t_forget == NULL); J_ASSERT(transaction->t_iobuf_list == NULL); J_ASSERT(transaction->t_shadow_list == NULL); J_ASSERT(transaction->t_log_list == NULL); J_ASSERT(transaction->t_checkpoint_list == NULL); J_ASSERT(transaction->t_updates == 0); J_ASSERT(journal->j_committing_transaction != transaction); J_ASSERT(journal->j_running_transaction != transaction); jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid); kfree(transaction); }