1 files changed, 241 insertions, 177 deletions

diff --git a/fs/jbd/checkpoint.c b/fs/jbd/checkpoint.c
index 014a51f..cb3cef5 100644
--- a/fs/jbd/checkpoint.c
+++ b/fs/jbd/checkpoint.c
@@ -24,29 +24,75 @@
 #include <linux/slab.h>
 
 /*
- * Unlink a buffer from a transaction. 
+ * Unlink a buffer from a transaction checkpoint list.
  *
  * Called with j_list_lock held.
  */
 
-static inline void __buffer_unlink(struct journal_head *jh)
+static void __buffer_unlink_first(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;
+		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;
 }
 
 /*
  * Try to release a checkpointed buffer from its transaction.
- * Returns 1 if we released it.
+ * Returns 1 if we released it and 2 if we also released the
+ * whole transaction.
+ *
  * Requires j_list_lock
  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  */
@@ -57,12 +103,11 @@ 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");
-		__journal_remove_checkpoint(jh);
+		ret = __journal_remove_checkpoint(jh) + 1;
 		jbd_unlock_bh_state(bh);
 		journal_remove_journal_head(bh);
 		BUFFER_TRACE(bh, "release");
 		__brelse(bh);
-		ret = 1;
 	} else {
 		jbd_unlock_bh_state(bh);
 	}
@@ -117,83 +162,53 @@ static void jbd_sync_bh(journal_t *journal, struct buffer_head *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)
+ * 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.
  *
  * Called with j_list_lock held.
  */
-static int __cleanup_transaction(journal_t *journal, transaction_t *transaction)
+
+static void __wait_cp_io(journal_t *journal, transaction_t *transaction)
 {
-	struct journal_head *jh, *next_jh, *last_jh;
+	struct journal_head *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;
+	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;
 		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);
-			goto out_return_1;
-		}
-
-		/*
-		 * This is foul
-		 */
-		if (!jbd_trylock_bh_state(bh)) {
-			jbd_sync_bh(journal, bh);
-			goto out_return_1;
+			spin_lock(&journal->j_list_lock);
+			goto restart;
 		}
-
-		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?
+		 * 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
 		 */
-		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;
+		released = __journal_remove_checkpoint(jh);
+		jbd_unlock_bh_state(bh);
+	}
 }
 
 #define NR_BATCH	64
@@ -203,9 +218,7 @@ __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);
@@ -221,19 +234,46 @@ __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.
+ * Called with j_list_lock held and drops it if 1 is returned
  * 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)
+static int __process_buffer(journal_t *journal, struct journal_head *jh,
+			struct buffer_head **bhs, int *batch_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);
+	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;
 
+		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.
@@ -246,45 +286,30 @@ static int __flush_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 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.
+ * 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.
  * 
- * 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");
 
@@ -299,79 +324,70 @@ int log_do_checkpoint(journal_t *journal)
 		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.
+	 * 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;
+	this_tid = transaction->t_tid;
+restart:
 	/*
-	 * AKPM: check this code.  I had a feeling a while back that it
-	 * degenerates into a busy loop at unmount time.
+	 * 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).
 	 */
-	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 {
+ 	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) {
 			struct buffer_head *bh;
 
-			jh = next_jh;
-			next_jh = jh->b_cpnext;
+			jh = transaction->t_checkpoint_list;
 			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 = __process_buffer(journal, jh, bhs,
+						&batch_count);
+			if (!retry &&
+			    lock_need_resched(&journal->j_list_lock)) {
+				spin_unlock(&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;
+		}
 		/*
-		 * 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. 
+		 * Now we have cleaned up the first transaction's checkpoint
+		 * list.  Let's clean up the second one.
 		 */
-		cleanup_ret = __cleanup_transaction(journal, transaction);
-		J_ASSERT(drop_count != 0 || cleanup_ret != 0);
-		if (journal->j_checkpoint_transactions != transaction)
-			break;
+		__wait_cp_io(journal, transaction);
 	}
+out:
 	spin_unlock(&journal->j_list_lock);
 	result = cleanup_journal_tail(journal);
 	if (result < 0)
 		return result;
-
 	return 0;
 }
 
@@ -456,52 +472,91 @@ 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 bufers reaped (for debug)
+ * Returns number of buffers reaped (for debug)
  */
 
 int __journal_clean_checkpoint_list(journal_t *journal)
 {
 	transaction_t *transaction, *last_transaction, *next_transaction;
-	int ret = 0;
+	int ret = 0, released;
 
 	transaction = journal->j_checkpoint_transactions;
-	if (transaction == 0)
+	if (!transaction)
 		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);
-		}
+		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;
 	} while (transaction != last_transaction);
 out:
 	return ret;
@@ -516,18 +571,22 @@ 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
- * list until they have been rewritten, at which point this function is
+ * lists until they have been rewritten, at which point this function is
  * called to remove the buffer from the existing transaction's
- * checkpoint list.  
+ * checkpoint lists.
+ *
+ * The function returns 1 if it frees the transaction, 0 otherwise.
  *
  * 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))
  */
 
-void __journal_remove_checkpoint(struct journal_head *jh)
+int __journal_remove_checkpoint(struct journal_head *jh)
 {
 	transaction_t *transaction;
 	journal_t *journal;
+	int ret = 0;
 
 	JBUFFER_TRACE(jh, "entry");
 
@@ -538,8 +597,10 @@ void __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)
+	if (transaction->t_checkpoint_list != NULL ||
+	    transaction->t_checkpoint_io_list != NULL)
 		goto out;
 	JBUFFER_TRACE(jh, "transaction has no more buffers");
 
@@ -565,8 +626,10 @@ void __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;
 }
 
 /*
@@ -628,6 +691,7 @@ 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);