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>

4 files changed, 57 insertions, 21 deletions

diff --git a/fs/ext3/fsync.c b/fs/ext3/fsync.c
index 451d166bbe93..8209f266e9ad 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
diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 069a163393b4..354ed3b47b30 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -699,8 +699,9 @@ static int ext3_splice_branch(handle_t *handle, struct inode *inode,
         int err = 0;
         struct ext3_block_alloc_info *block_i;
         ext3_fsblk_t current_block;
+        struct ext3_inode_info *ei = EXT3_I(inode);
 
-        block_i = EXT3_I(inode)->i_block_alloc_info;
+        block_i = ei->i_block_alloc_info;
         /*
          * If we're splicing into a [td]indirect block (as opposed to the
          * inode) then we need to get write access to the [td]indirect block
@@ -741,6 +742,8 @@ static int ext3_splice_branch(handle_t *handle, struct inode *inode,
 
         inode->i_ctime = CURRENT_TIME_SEC;
         ext3_mark_inode_dirty(handle, inode);
+        /* ext3_mark_inode_dirty already updated i_sync_tid */
+        atomic_set(&ei->i_datasync_tid, handle->h_transaction->t_tid);
 
         /* had we spliced it onto indirect block? */
         if (where->bh) {
@@ -2754,6 +2757,8 @@ struct inode *ext3_iget(struct super_block *sb, unsigned long ino)
         struct ext3_inode_info *ei;
         struct buffer_head *bh;
         struct inode *inode;
+        journal_t *journal = EXT3_SB(sb)->s_journal;
+        transaction_t *transaction;
         long ret;
         int block;
 
@@ -2831,6 +2836,30 @@ struct inode *ext3_iget(struct super_block *sb, unsigned long ino)
                 ei->i_data[block] = raw_inode->i_block[block];
         INIT_LIST_HEAD(&ei->i_orphan);
 
+        /*
+         * Set transaction id's of transactions that have to be committed
+         * to finish f[data]sync. We set them to currently running transaction
+         * as we cannot be sure that the inode or some of its metadata isn't
+         * part of the transaction - the inode could have been reclaimed and
+         * now it is reread from disk.
+         */
+        if (journal) {
+                tid_t tid;
+
+                spin_lock(&journal->j_state_lock);
+                if (journal->j_running_transaction)
+                        transaction = journal->j_running_transaction;
+                else
+                        transaction = journal->j_committing_transaction;
+                if (transaction)
+                        tid = transaction->t_tid;
+                else
+                        tid = journal->j_commit_sequence;
+                spin_unlock(&journal->j_state_lock);
+                atomic_set(&ei->i_sync_tid, tid);
+                atomic_set(&ei->i_datasync_tid, tid);
+        }
+
         if (inode->i_ino >= EXT3_FIRST_INO(inode->i_sb) + 1 &&
             EXT3_INODE_SIZE(inode->i_sb) > EXT3_GOOD_OLD_INODE_SIZE) {
                 /*
@@ -3015,6 +3044,7 @@ again:
                 err = rc;
         ei->i_state &= ~EXT3_STATE_NEW;
 
+        atomic_set(&ei->i_sync_tid, handle->h_transaction->t_tid);
 out_brelse:
         brelse (bh);
         ext3_std_error(inode->i_sb, err);
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 7a520a862f49..427496c4767c 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -466,6 +466,8 @@ static struct inode *ext3_alloc_inode(struct super_block *sb)
                 return NULL;
         ei->i_block_alloc_info = NULL;
         ei->vfs_inode.i_version = 1;
+        atomic_set(&ei->i_datasync_tid, 0);
+        atomic_set(&ei->i_sync_tid, 0);
         return &ei->vfs_inode;
 }
 
diff --git a/include/linux/ext3_fs_i.h b/include/linux/ext3_fs_i.h
index ca1bfe90004f..93e7428156ba 100644
--- a/include/linux/ext3_fs_i.h
+++ b/include/linux/ext3_fs_i.h
@@ -137,6 +137,14 @@ struct ext3_inode_info {
          * by other means, so we have truncate_mutex.
          */
         struct mutex truncate_mutex;
+
+        /*
+         * Transactions that contain inode's metadata needed to complete
+         * fsync and fdatasync, respectively.
+         */
+        atomic_t i_sync_tid;
+        atomic_t i_datasync_tid;
+
         struct inode vfs_inode;
 };