Date:	Wed, 4 Jun 2008 17:57:03 +0200
From:	Jan Kara <jack@...e.cz>
To:	linux-ext4@...r.kernel.org
Subject: [PATCH 3/5] jbd2: Implement data=ordered mode handling via inodes

From: Jan Kara <jack@...e.cz>
Date: Wed, 21 May 2008 17:48:42 +0200
Subject: [PATCH] jbd2: Implement data=ordered mode handling via inodes

This patch adds necessary framework into JBD2 to be able to track inodes
with each transaction and write-out their dirty data during transaction
commit time.

Signed-off-by: Jan Kara <jack@...e.cz>
---
 fs/jbd2/commit.c      |   90 +++++++++++++++++++++++++++++++++++++++++++++++++
 fs/jbd2/journal.c     |   52 ++++++++++++++++++++++++++++
 fs/jbd2/transaction.c |   86 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/jbd2.h  |   42 +++++++++++++++++++++++
 4 files changed, 270 insertions(+), 0 deletions(-)

Index: linux-2.6-linus/fs/jbd2/commit.c
===================================================================
--- linux-2.6-linus.orig/fs/jbd2/commit.c
+++ linux-2.6-linus/fs/jbd2/commit.c
@@ -354,6 +354,81 @@ write_out_data:
 	journal_do_submit_data(wbuf, bufs);
 }
 
+/*
+ * Submit all the data buffers of inode associated with the transaction to
+ * disk.
+ *
+ * We are in a committing transaction. Therefore no new inode can be added to
+ * our inode list. We use JI_COMMIT_RUNNING flag to protect inode we currently
+ * operate on from being released while we write out pages.
+ */
+static int journal_submit_inode_data_buffers(journal_t *journal,
+		transaction_t *commit_transaction)
+{
+	struct jbd2_inode *jinode;
+	int err, ret = 0;
+	struct address_space *mapping;
+
+	spin_lock(&journal->j_list_lock);
+	list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
+		mapping = jinode->i_vfs_inode->i_mapping;
+		jinode->i_flags |= JI_COMMIT_RUNNING;
+		spin_unlock(&journal->j_list_lock);
+		err = filemap_fdatawrite_range(mapping, 0,
+					i_size_read(jinode->i_vfs_inode));
+		if (!ret)
+			ret = err;
+		spin_lock(&journal->j_list_lock);
+		J_ASSERT(jinode->i_transaction == commit_transaction);
+		jinode->i_flags &= ~JI_COMMIT_RUNNING;
+		wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
+	}
+	spin_unlock(&journal->j_list_lock);
+	return ret;
+}
+
+/*
+ * Wait for data submitted for writeout, refile inodes to proper
+ * transaction if needed.
+ *
+ */
+static int journal_finish_inode_data_buffers(journal_t *journal,
+		transaction_t *commit_transaction)
+{
+	struct jbd2_inode *jinode, *next_i;
+	int err, ret = 0;
+
+	/* For locking, see the comment in journal_submit_inode_data_buffers() */
+	spin_lock(&journal->j_list_lock);
+	list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
+		jinode->i_flags |= JI_COMMIT_RUNNING;
+		spin_unlock(&journal->j_list_lock);
+		err = filemap_fdatawait(jinode->i_vfs_inode->i_mapping);
+		if (!ret)
+			ret = err;
+		spin_lock(&journal->j_list_lock);
+		jinode->i_flags &= ~JI_COMMIT_RUNNING;
+		wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
+	}
+
+	/* Now refile inode to proper lists */
+	list_for_each_entry_safe(jinode, next_i,
+				 &commit_transaction->t_inode_list, i_list) {
+		list_del(&jinode->i_list);
+		if (jinode->i_next_transaction) {
+			jinode->i_transaction = jinode->i_next_transaction;
+			jinode->i_next_transaction = NULL;
+			list_add(&jinode->i_list,
+				&jinode->i_transaction->t_inode_list);
+		} else {
+			jinode->i_transaction = NULL;
+		}
+	}
+	spin_unlock(&journal->j_list_lock);
+
+	return ret;
+}
+
 static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
 {
 	struct page *page = bh->b_page;
@@ -528,6 +603,9 @@ void jbd2_journal_commit_transaction(jou
 	 */
 	err = 0;
 	journal_submit_data_buffers(journal, commit_transaction);
+	err = journal_submit_inode_data_buffers(journal, commit_transaction);
+	if (err)
+		jbd2_journal_abort(journal, err);
 
 	/*
 	 * Wait for all previously submitted IO to complete if commit
@@ -759,6 +837,17 @@ start_journal_io:
 			__jbd2_journal_abort_hard(journal);
 	}
 
+	/*
+	 * This is the right place to wait for data buffers both for ASYNC
+	 * and !ASYNC commit. If commit is ASYNC, we need to wait only after
+	 * the commit block went to disk (which happens above). If commit is
+	 * SYNC, we need to wait for data buffers before we start writing
+	 * commit block, which happens below in such setting.
+	 */
+	err = journal_finish_inode_data_buffers(journal, commit_transaction);
+	if (err)
+		jbd2_journal_abort(journal, err);
+
 	/* Lo and behold: we have just managed to send a transaction to
            the log.  Before we can commit it, wait for the IO so far to
            complete.  Control buffers being written are on the
@@ -879,6 +968,7 @@ wait_for_iobuf:
 	jbd_debug(3, "JBD: commit phase 7\n");
 
 	J_ASSERT(commit_transaction->t_sync_datalist == NULL);
+	J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 	J_ASSERT(commit_transaction->t_buffers == NULL);
 	J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 	J_ASSERT(commit_transaction->t_iobuf_list == NULL);
Index: linux-2.6-linus/fs/jbd2/journal.c
===================================================================
--- linux-2.6-linus.orig/fs/jbd2/journal.c
+++ linux-2.6-linus/fs/jbd2/journal.c
@@ -82,6 +82,10 @@ EXPORT_SYMBOL(jbd2_journal_blocks_per_pa
 EXPORT_SYMBOL(jbd2_journal_invalidatepage);
 EXPORT_SYMBOL(jbd2_journal_try_to_free_buffers);
 EXPORT_SYMBOL(jbd2_journal_force_commit);
+EXPORT_SYMBOL(jbd2_journal_file_inode);
+EXPORT_SYMBOL(jbd2_journal_init_jbd_inode);
+EXPORT_SYMBOL(jbd2_journal_release_jbd_inode);
+EXPORT_SYMBOL(jbd2_journal_begin_ordered_truncate);
 
 static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
 static void __journal_abort_soft (journal_t *journal, int errno);
@@ -2195,6 +2199,54 @@ void jbd2_journal_put_journal_head(struc
 }
 
 /*
+ * Initialize jbd inode head
+ */
+void jbd2_journal_init_jbd_inode(struct jbd2_inode *jinode, struct inode *inode)
+{
+	jinode->i_transaction = NULL;
+	jinode->i_next_transaction = NULL;
+	jinode->i_vfs_inode = inode;
+	jinode->i_flags = 0;
+	INIT_LIST_HEAD(&jinode->i_list);
+}
+
+/*
+ * Function to be called before we start removing inode from memory (i.e.,
+ * clear_inode() is a fine place to be called from). It removes inode from
+ * transaction's lists.
+ */
+void jbd2_journal_release_jbd_inode(journal_t *journal,
+				    struct jbd2_inode *jinode)
+{
+	int writeout = 0;
+
+	if (!journal)
+		return;
+restart:
+	spin_lock(&journal->j_list_lock);
+	/* Is commit writing out inode - we have to wait */
+	if (jinode->i_flags & JI_COMMIT_RUNNING) {
+		wait_queue_head_t *wq;
+		DEFINE_WAIT_BIT(wait, &jinode->i_flags, __JI_COMMIT_RUNNING);
+		wq = bit_waitqueue(&jinode->i_flags, __JI_COMMIT_RUNNING);
+		prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
+		spin_unlock(&journal->j_list_lock);
+		schedule();
+		finish_wait(wq, &wait.wait);
+		goto restart;
+	}
+
+	/* Do we need to wait for data writeback? */
+	if (journal->j_committing_transaction == jinode->i_transaction)
+		writeout = 1;
+	if (jinode->i_transaction) {
+		list_del(&jinode->i_list);
+		jinode->i_transaction = NULL;
+	}
+	spin_unlock(&journal->j_list_lock);
+}
+
+/*
  * debugfs tunables
  */
 #ifdef CONFIG_JBD2_DEBUG
Index: linux-2.6-linus/fs/jbd2/transaction.c
===================================================================
--- linux-2.6-linus.orig/fs/jbd2/transaction.c
+++ linux-2.6-linus/fs/jbd2/transaction.c
@@ -51,6 +51,7 @@ jbd2_get_transaction(journal_t *journal,
 	transaction->t_tid = journal->j_transaction_sequence++;
 	transaction->t_expires = jiffies + journal->j_commit_interval;
 	spin_lock_init(&transaction->t_handle_lock);
+	INIT_LIST_HEAD(&transaction->t_inode_list);
 
 	/* Set up the commit timer for the new transaction. */
 	journal->j_commit_timer.expires = round_jiffies(transaction->t_expires);
@@ -2195,3 +2196,88 @@ void jbd2_journal_refile_buffer(journal_
 	spin_unlock(&journal->j_list_lock);
 	__brelse(bh);
 }
+
+/*
+ * File inode in the inode list of the handle's transaction
+ */
+int jbd2_journal_file_inode(handle_t *handle, struct jbd2_inode *jinode)
+{
+	transaction_t *transaction = handle->h_transaction;
+	journal_t *journal = transaction->t_journal;
+
+	if (is_handle_aborted(handle))
+		return -EIO;
+
+	jbd_debug(4, "Adding inode %lu, tid:%d\n", jinode->i_vfs_inode->i_ino,
+			transaction->t_tid);
+
+	/*
+	 * First check whether inode isn't already on the transaction's
+	 * lists without taking the lock. Note that this check is safe
+	 * without the lock as we cannot race with somebody removing inode
+	 * from the transaction. The reason is that we remove inode from the
+	 * transaction only in journal_release_jbd_inode() and when we commit
+	 * the transaction. We are guarded from the first case by holding
+	 * a reference to the inode. We are safe against the second case
+	 * because if jinode->i_transaction == transaction, commit code
+	 * cannot touch the transaction because we hold reference to it,
+	 * and if jinode->i_next_transaction == transaction, commit code
+	 * will only file the inode where we want it.
+	 */
+	if (jinode->i_transaction == transaction ||
+	    jinode->i_next_transaction == transaction)
+		return 0;
+
+	spin_lock(&journal->j_list_lock);
+
+	if (jinode->i_transaction == transaction ||
+	    jinode->i_next_transaction == transaction)
+		goto done;
+
+	/* On some different transaction's list - should be
+	 * the committing one */
+	if (jinode->i_transaction) {
+		J_ASSERT(jinode->i_next_transaction == NULL);
+		J_ASSERT(jinode->i_transaction ==
+					journal->j_committing_transaction);
+		jinode->i_next_transaction = transaction;
+		goto done;
+	}
+	/* Not on any transaction list... */
+	J_ASSERT(!jinode->i_next_transaction);
+	jinode->i_transaction = transaction;
+	list_add(&jinode->i_list, &transaction->t_inode_list);
+done:
+	spin_unlock(&journal->j_list_lock);
+
+	return 0;
+}
+
+/*
+ * This function must be called when inode is journaled in ordered mode
+ * before truncation happens. It starts writeout of truncated part in
+ * case it is in the committing transaction so that we stand to ordered
+ * mode consistency guarantees.
+ */
+int jbd2_journal_begin_ordered_truncate(struct jbd2_inode *inode,
+					loff_t new_size)
+{
+	journal_t *journal;
+	transaction_t *commit_trans;
+	int ret = 0;
+
+	if (!inode->i_transaction && !inode->i_next_transaction)
+		goto out;
+	journal = inode->i_transaction->t_journal;
+	spin_lock(&journal->j_state_lock);
+	commit_trans = journal->j_committing_transaction;
+	spin_unlock(&journal->j_state_lock);
+	if (inode->i_transaction == commit_trans) {
+		ret = filemap_fdatawrite_range(inode->i_vfs_inode->i_mapping,
+			new_size, LLONG_MAX);
+		if (ret)
+			jbd2_journal_abort(journal, ret);
+	}
+out:
+	return ret;
+}
Index: linux-2.6-linus/include/linux/jbd2.h
===================================================================
--- linux-2.6-linus.orig/include/linux/jbd2.h
+++ linux-2.6-linus/include/linux/jbd2.h
@@ -381,6 +381,38 @@ static inline void jbd_unlock_bh_journal
 	bit_spin_unlock(BH_JournalHead, &bh->b_state);
 }
 
+/* Flags in jbd_inode->i_flags */
+#define __JI_COMMIT_RUNNING 0
+/* Commit of the inode data in progress. We use this flag to protect us from
+ * concurrent deletion of inode. We cannot use reference to inode for this
+ * since we cannot afford doing last iput() on behalf of kjournald
+ */
+#define JI_COMMIT_RUNNING (1 << __JI_COMMIT_RUNNING)
+
+/**
+ * struct jbd_inode is the structure linking inodes in ordered mode
+ *   present in a transaction so that we can sync them during commit.
+ */
+struct jbd2_inode {
+	/* Which transaction does this inode belong to? Either the running
+	 * transaction or the committing one. [j_list_lock] */
+	transaction_t *i_transaction;
+
+	/* Pointer to the running transaction modifying inode's data in case
+	 * there is already a committing transaction touching it. [j_list_lock] */
+	transaction_t *i_next_transaction;
+
+	/* List of inodes in the i_transaction [j_list_lock] */
+	struct list_head i_list;
+
+	/* VFS inode this inode belongs to [constant during the lifetime
+	 * of the structure] */
+	struct inode *i_vfs_inode;
+
+	/* Flags of inode [j_list_lock] */
+	unsigned int i_flags;
+};
+
 struct jbd2_revoke_table_s;
 
 /**
@@ -567,6 +599,12 @@ struct transaction_s
 	struct journal_head	*t_log_list;
 
 	/*
+	 * List of inodes whose data we've modified in data=ordered mode.
+	 * [j_list_lock]
+	 */
+	struct list_head	t_inode_list;
+
+	/*
 	 * Protects info related to handles
 	 */
 	spinlock_t		t_handle_lock;
@@ -1043,6 +1081,10 @@ extern void	   jbd2_journal_ack_err    (
 extern int	   jbd2_journal_clear_err  (journal_t *);
 extern int	   jbd2_journal_bmap(journal_t *, unsigned long, unsigned long long *);
 extern int	   jbd2_journal_force_commit(journal_t *);
+extern int	   jbd2_journal_file_inode(handle_t *handle, struct jbd2_inode *inode);
+extern int	   jbd2_journal_begin_ordered_truncate(struct jbd2_inode *inode, loff_t new_size);
+extern void	   jbd2_journal_init_jbd_inode(struct jbd2_inode *jinode, struct inode *inode);
+extern void	   jbd2_journal_release_jbd_inode(journal_t *journal, struct jbd2_inode *jinode);
 
 /*
  * journal_head management
--
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