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-rw-r--r--fs/jbd/checkpoint.c636
1 files changed, 636 insertions, 0 deletions
diff --git a/fs/jbd/checkpoint.c b/fs/jbd/checkpoint.c
new file mode 100644
index 00000000000..98d830401c5
--- /dev/null
+++ b/fs/jbd/checkpoint.c
@@ -0,0 +1,636 @@
+/*
+ * 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);
+ }
+ jh = next_jh;
+ } 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(WRITE, *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);
+
+ /*
+ * 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);
+}
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