1 files changed, 177 insertions, 241 deletions

diff --git a/fs/jbd/checkpoint.c b/fs/jbd/checkpoint.c
index e6265a0..543ed54 100644
--- a/fs/jbd/checkpoint.c
+++ b/fs/jbd/checkpoint.c
@@ -24,75 +24,29 @@
 #include <linux/slab.h>
 
 /*
- * Unlink a buffer from a transaction checkpoint list.
+ * Unlink a buffer from a transaction.
  *
  * Called with j_list_lock held.
  */
 
-static void __buffer_unlink_first(struct journal_head *jh)
+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) {
+	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;
-
-	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;
-
-	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;
+	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 and 2 if we also released the
- * whole transaction.
- *
+ * Returns 1 if we released it.
  * Requires j_list_lock
  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  */
@@ -103,11 +57,12 @@ static int __try_to_free_cp_buf(struct journal_head *jh)
 
 	if (jh->b_jlist == BJ_None && !buffer_locked(bh) && !buffer_dirty(bh)) {
 		JBUFFER_TRACE(jh, "remove from checkpoint list");
-		ret = __journal_remove_checkpoint(jh) + 1;
+		__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);
 	}
@@ -162,53 +117,83 @@ static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)
 }
 
 /*
- * Clean up transaction's list of buffers submitted for io.
- * We wait for any pending IO to complete and remove any clean
- * buffers. Note that we take the buffers in the opposite ordering
- * from the one in which they were submitted for IO.
+ * 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 void __wait_cp_io(journal_t *journal, transaction_t *transaction)
+static int __cleanup_transaction(journal_t *journal, transaction_t *transaction)
 {
-	struct journal_head *jh;
+	struct journal_head *jh, *next_jh, *last_jh;
 	struct buffer_head *bh;
-	tid_t this_tid;
-	int released = 0;
-
-	this_tid = transaction->t_tid;
-restart:
-	/* Didn't somebody clean up the transaction in the meanwhile */
-	if (journal->j_checkpoint_transactions != transaction ||
-		transaction->t_tid != this_tid)
-		return;
-	while (!released && transaction->t_checkpoint_io_list) {
-		jh = transaction->t_checkpoint_io_list;
+	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 (!jbd_trylock_bh_state(bh)) {
-			jbd_sync_bh(journal, bh);
-			spin_lock(&journal->j_list_lock);
-			goto restart;
-		}
 		if (buffer_locked(bh)) {
 			atomic_inc(&bh->b_count);
 			spin_unlock(&journal->j_list_lock);
-			jbd_unlock_bh_state(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 restart;
+			goto out_return_1;
 		}
+
 		/*
-		 * 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
+		 * This is foul
 		 */
-		released = __journal_remove_checkpoint(jh);
-		jbd_unlock_bh_state(bh);
-	}
+		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
@@ -218,7 +203,9 @@ __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);
@@ -234,46 +221,19 @@ __flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
  * Return 1 if something happened which requires us to abort the current
  * scan of the checkpoint list.  
  *
- * Called with j_list_lock held and drops it if 1 is returned
+ * Called with j_list_lock held.
  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  */
-static int __process_buffer(journal_t *journal, struct journal_head *jh,
-			struct buffer_head **bhs, int *batch_count)
+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_locked(bh)) {
-		get_bh(bh);
-		spin_unlock(&journal->j_list_lock);
-		jbd_unlock_bh_state(bh);
-		wait_on_buffer(bh);
-		/* the journal_head may have gone by now */
-		BUFFER_TRACE(bh, "brelse");
-		put_bh(bh);
-		ret = 1;
-	}
-	else if (jh->b_transaction != NULL) {
-		transaction_t *t = jh->b_transaction;
-		tid_t tid = t->t_tid;
+	if (buffer_dirty(bh) && !buffer_locked(bh) && jh->b_jlist == BJ_None) {
+		J_ASSERT_JH(jh, jh->b_transaction == NULL);
 
-		spin_unlock(&journal->j_list_lock);
-		jbd_unlock_bh_state(bh);
-		log_start_commit(journal, tid);
-		log_wait_commit(journal, tid);
-		ret = 1;
-	}
-	else if (!buffer_dirty(bh)) {
-		J_ASSERT_JH(jh, !buffer_jbddirty(bh));
-		BUFFER_TRACE(bh, "remove from checkpoint");
-		__journal_remove_checkpoint(jh);
-		spin_unlock(&journal->j_list_lock);
-		jbd_unlock_bh_state(bh);
-		journal_remove_journal_head(bh);
-		put_bh(bh);
-		ret = 1;
-	}
-	else {
 		/*
 		 * Important: we are about to write the buffer, and
 		 * possibly block, while still holding the journal lock.
@@ -286,30 +246,45 @@ static int __process_buffer(journal_t *journal, struct journal_head *jh,
 		J_ASSERT_BH(bh, !buffer_jwrite(bh));
 		set_buffer_jwrite(bh);
 		bhs[*batch_count] = bh;
-		__buffer_relink_io(jh);
 		jbd_unlock_bh_state(bh);
 		(*batch_count)++;
 		if (*batch_count == NR_BATCH) {
-			spin_unlock(&journal->j_list_lock);
 			__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 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.
+ * 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)
 {
-	transaction_t *transaction;
-	tid_t this_tid;
 	int result;
+	int batch_count = 0;
+	struct buffer_head *bhs[NR_BATCH];
 
 	jbd_debug(1, "Start checkpoint\n");
 
@@ -324,70 +299,79 @@ int log_do_checkpoint(journal_t *journal)
 		return result;
 
 	/*
-	 * OK, we need to start writing disk blocks.  Take one transaction
-	 * and write it.
+	 * OK, we need to start writing disk blocks.  Try to free up a
+	 * quarter of the log in a single checkpoint if we can.
 	 */
-	spin_lock(&journal->j_list_lock);
-	if (!journal->j_checkpoint_transactions)
-		goto out;
-	transaction = journal->j_checkpoint_transactions;
-	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).
+	 * AKPM: check this code.  I had a feeling a while back that it
+	 * degenerates into a busy loop at unmount time.
 	 */
- 	if (journal->j_checkpoint_transactions == transaction &&
-			transaction->t_tid == this_tid) {
-		int batch_count = 0;
-		struct buffer_head *bhs[NR_BATCH];
-		struct journal_head *jh;
-		int retry = 0;
-
-		while (!retry && transaction->t_checkpoint_list) {
+	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 = transaction->t_checkpoint_list;
+			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 = __process_buffer(journal, jh, bhs,
-						&batch_count);
-			if (!retry &&
-			    lock_need_resched(&journal->j_list_lock)) {
-				spin_unlock(&journal->j_list_lock);
+			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) {
-			if (!retry) {
-				spin_unlock(&journal->j_list_lock);
-				retry = 1;
-			}
 			__flush_batch(journal, bhs, &batch_count);
+			retry = 1;
 		}
 
-		if (retry) {
-			spin_lock(&journal->j_list_lock);
-			goto restart;
-		}
 		/*
-		 * Now we have cleaned up the first transaction's checkpoint
-		 * list.  Let's clean up the second one.
+		 * 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
 		 */
-		__wait_cp_io(journal, transaction);
+		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;
 	}
-out:
 	spin_unlock(&journal->j_list_lock);
 	result = cleanup_journal_tail(journal);
 	if (result < 0)
 		return result;
+
 	return 0;
 }
 
@@ -472,91 +456,52 @@ int cleanup_journal_tail(journal_t *journal)
 /* Checkpoint list management */
 
 /*
- * journal_clean_one_cp_list
- *
- * Find all the written-back checkpoint buffers in the given list and release them.
- *
- * Called with the journal locked.
- * Called with j_list_lock held.
- * Returns number of bufers reaped (for debug)
- */
-
-static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
-{
-	struct journal_head *last_jh;
-	struct journal_head *next_jh = jh;
-	int ret, freed = 0;
-
-	*released = 0;
-	if (!jh)
-		return 0;
-
- 	last_jh = jh->b_cpprev;
-	do {
-		jh = next_jh;
-		next_jh = jh->b_cpnext;
-		/* Use trylock because of the ranking */
-		if (jbd_trylock_bh_state(jh2bh(jh))) {
-			ret = __try_to_free_cp_buf(jh);
-			if (ret) {
-				freed++;
-				if (ret == 2) {
-					*released = 1;
-					return freed;
-				}
-			}
-		}
-		/*
-		 * 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 the journal locked.
  * Called with j_list_lock held.
- * Returns number of buffers reaped (for debug)
+ * 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, released;
+	int ret = 0;
 
 	transaction = journal->j_checkpoint_transactions;
-	if (!transaction)
+	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;
-		ret += journal_clean_one_cp_list(transaction->
-				t_checkpoint_list, &released);
-		if (need_resched())
-			goto out;
-		if (released)
-			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, &released);
-		if (need_resched())
-			goto out;
+		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;
@@ -571,22 +516,18 @@ out:
  * 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
+ * list 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.
+ * checkpoint list.
  *
  * This function is called with the journal locked.
  * This function is called with j_list_lock held.
- * This function is called with jbd_lock_bh_state(jh2bh(jh))
  */
 
-int __journal_remove_checkpoint(struct journal_head *jh)
+void __journal_remove_checkpoint(struct journal_head *jh)
 {
 	transaction_t *transaction;
 	journal_t *journal;
-	int ret = 0;
 
 	JBUFFER_TRACE(jh, "entry");
 
@@ -597,10 +538,8 @@ int __journal_remove_checkpoint(struct journal_head *jh)
 	journal = transaction->t_journal;
 
 	__buffer_unlink(jh);
-	jh->b_cp_transaction = NULL;
 
-	if (transaction->t_checkpoint_list != NULL ||
-	    transaction->t_checkpoint_io_list != NULL)
+	if (transaction->t_checkpoint_list != NULL)
 		goto out;
 	JBUFFER_TRACE(jh, "transaction has no more buffers");
 
@@ -626,10 +565,8 @@ int __journal_remove_checkpoint(struct journal_head *jh)
 	/* Just in case anybody was waiting for more transactions to be
            checkpointed... */
 	wake_up(&journal->j_wait_logspace);
-	ret = 1;
 out:
 	JBUFFER_TRACE(jh, "exit");
-	return ret;
 }
 
 /*
@@ -691,7 +628,6 @@ void __journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 	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_checkpoint_io_list == NULL);
 	J_ASSERT(transaction->t_updates == 0);
 	J_ASSERT(journal->j_committing_transaction != transaction);
 	J_ASSERT(journal->j_running_transaction != transaction);