ext4: 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>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 17 insertions, 29 deletions

diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
index a3c25076aef1..0b22497d92e1 100644
--- a/fs/ext4/fsync.c
+++ b/fs/ext4/fsync.c
@@ -51,25 +51,30 @@
 int ext4_sync_file(struct file *file, struct dentry *dentry, int datasync)
 {
         struct inode *inode = dentry->d_inode;
+        struct ext4_inode_info *ei = EXT4_I(inode);
         journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
-        int err, ret = 0;
+        int ret;
+        tid_t commit_tid;
 
         J_ASSERT(ext4_journal_current_handle() == NULL);
 
         trace_ext4_sync_file(file, dentry, datasync);
 
+        if (inode->i_sb->s_flags & MS_RDONLY)
+                return 0;
+
         ret = flush_aio_dio_completed_IO(inode);
         if (ret < 0)
                 return ret;
+        
+        if (!journal)
+                return simple_fsync(file, dentry, datasync);
+
         /*
-         * 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 proper transaction to
+         *  commit here.
          *
          * data=journal:
          *  filemap_fdatawrite won't do anything (the buffers are clean).
@@ -82,27 +87,10 @@ int ext4_sync_file(struct file *file, struct dentry *dentry, int datasync)
         if (ext4_should_journal_data(inode))
                 return ext4_force_commit(inode->i_sb);
 
-        if (!journal)
-                ret = sync_mapping_buffers(inode->i_mapping);
-
-        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
-                goto out;
-
-        /*
-         * 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 */
-                };
-                err = sync_inode(inode, &wbc);
-                if (ret == 0)
-                        ret = err;
-        }
-out:
-        if (journal && (journal->j_flags & JBD2_BARRIER))
+        commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
+        if (jbd2_log_start_commit(journal, commit_tid))
+                jbd2_log_wait_commit(journal, commit_tid);
+        else if (journal->j_flags & JBD2_BARRIER)
                 blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
         return ret;
 }