ext3: Wait for proper transaction commit on fsync

We cannot rely on buffer dirty bits during fsync because pdflush can come
before fsync is called and clear dirty bits without forcing a transaction
commit. What we do is that we track which transaction has last changed
the inode and which transaction last changed allocation and force it to
disk on fsync.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

1 files changed, 16 insertions, 20 deletions

diff --git a/fs/ext3/fsync.c b/fs/ext3/fsync.c
index 451d166..8209f26 100644
--- a/fs/ext3/fsync.c
+++ b/fs/ext3/fsync.c
@@ -46,19 +46,21 @@
 int ext3_sync_file(struct file * file, struct dentry *dentry, int datasync)
 {
 	struct inode *inode = dentry->d_inode;
+	struct ext3_inode_info *ei = EXT3_I(inode);
+	journal_t *journal = EXT3_SB(inode->i_sb)->s_journal;
 	int ret = 0;
+	tid_t commit_tid;
+
+	if (inode->i_sb->s_flags & MS_RDONLY)
+		return 0;
 
 	J_ASSERT(ext3_journal_current_handle() == NULL);
 
 	/*
-	 * data=writeback:
+	 * data=writeback,ordered:
 	 *  The caller's filemap_fdatawrite()/wait will sync the data.
-	 *  sync_inode() will sync the metadata
-	 *
-	 * data=ordered:
-	 *  The caller's filemap_fdatawrite() will write the data and
-	 *  sync_inode() will write the inode if it is dirty.  Then the caller's
-	 *  filemap_fdatawait() will wait on the pages.
+	 *  Metadata is in the journal, we wait for a proper transaction
+	 *  to commit here.
 	 *
 	 * data=journal:
 	 *  filemap_fdatawrite won't do anything (the buffers are clean).
@@ -73,22 +75,16 @@ int ext3_sync_file(struct file * file, struct dentry *dentry, int datasync)
 		goto out;
 	}
 
-	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
-		goto flush;
+	if (datasync)
+		commit_tid = atomic_read(&ei->i_datasync_tid);
+	else
+		commit_tid = atomic_read(&ei->i_sync_tid);
 
-	/*
-	 * The VFS has written the file data.  If the inode is unaltered
-	 * then we need not start a commit.
-	 */
-	if (inode->i_state & (I_DIRTY_SYNC|I_DIRTY_DATASYNC)) {
-		struct writeback_control wbc = {
-			.sync_mode = WB_SYNC_ALL,
-			.nr_to_write = 0, /* sys_fsync did this */
-		};
-		ret = sync_inode(inode, &wbc);
+	if (log_start_commit(journal, commit_tid)) {
+		log_wait_commit(journal, commit_tid);
 		goto out;
 	}
-flush:
+
 	/*
 	 * In case we didn't commit a transaction, we have to flush
 	 * disk caches manually so that data really is on persistent