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>

6 files changed, 80 insertions, 31 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 4cfc2f0edb3f..ab31e65d46d0 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -709,6 +709,13 @@ struct ext4_inode_info {
         struct list_head i_aio_dio_complete_list;
         /* current io_end structure for async DIO write*/
         ext4_io_end_t *cur_aio_dio;
+
+        /*
+         * Transactions that contain inode's metadata needed to complete
+         * fsync and fdatasync, respectively.
+         */
+        tid_t i_sync_tid;
+        tid_t i_datasync_tid;
 };
 
 /*
diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index 2c2b262bd31b..05eca817d704 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -249,6 +249,19 @@ static inline int ext4_jbd2_file_inode(handle_t *handle, struct inode *inode)
         return 0;
 }
 
+static inline void ext4_update_inode_fsync_trans(handle_t *handle,
+                                                 struct inode *inode,
+                                                 int datasync)
+{
+        struct ext4_inode_info *ei = EXT4_I(inode);
+
+        if (ext4_handle_valid(handle)) {
+                ei->i_sync_tid = handle->h_transaction->t_tid;
+                if (datasync)
+                        ei->i_datasync_tid = handle->h_transaction->t_tid;
+        }
+}
+
 /* super.c */
 int ext4_force_commit(struct super_block *sb);
 
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 5967f18fd7e7..700206e525da 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3058,6 +3058,8 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
         if (flags == EXT4_GET_BLOCKS_DIO_CONVERT_EXT) {
                 ret = ext4_convert_unwritten_extents_dio(handle, inode,
                                                         path);
+                if (ret >= 0)
+                        ext4_update_inode_fsync_trans(handle, inode, 1);
                 goto out2;
         }
         /* buffered IO case */
@@ -3085,6 +3087,8 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
         ret = ext4_ext_convert_to_initialized(handle, inode,
                                                 path, iblock,
                                                 max_blocks);
+        if (ret >= 0)
+                ext4_update_inode_fsync_trans(handle, inode, 1);
 out:
         if (ret <= 0) {
                 err = ret;
@@ -3323,10 +3327,16 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
         allocated = ext4_ext_get_actual_len(&newex);
         set_buffer_new(bh_result);
 
-        /* Cache only when it is _not_ an uninitialized extent */
-        if ((flags & EXT4_GET_BLOCKS_UNINIT_EXT) == 0)
+        /*
+         * Cache the extent and update transaction to commit on fdatasync only
+         * when it is _not_ an uninitialized extent.
+         */
+        if ((flags & EXT4_GET_BLOCKS_UNINIT_EXT) == 0) {
                 ext4_ext_put_in_cache(inode, iblock, allocated, newblock,
                                                 EXT4_EXT_CACHE_EXTENT);
+                ext4_update_inode_fsync_trans(handle, inode, 1);
+        } else
+                ext4_update_inode_fsync_trans(handle, inode, 0);
 out:
         if (allocated > max_blocks)
                 allocated = max_blocks;
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;
 }
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 958c3ff800e9..f1bc1e338828 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -983,6 +983,8 @@ static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode,
                 goto cleanup;
 
         set_buffer_new(bh_result);
+
+        ext4_update_inode_fsync_trans(handle, inode, 1);
 got_it:
         map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
         if (count > blocks_to_boundary)
@@ -4738,6 +4740,7 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
         struct ext4_inode *raw_inode;
         struct ext4_inode_info *ei;
         struct inode *inode;
+        journal_t *journal = EXT4_SB(sb)->s_journal;
         long ret;
         int block;
 
@@ -4802,6 +4805,31 @@ struct inode *ext4_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) {
+                transaction_t *transaction;
+                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);
+                ei->i_sync_tid = tid;
+                ei->i_datasync_tid = tid;
+        }
+
         if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
                 ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
                 if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >
@@ -5056,6 +5084,7 @@ static int ext4_do_update_inode(handle_t *handle,
                 err = rc;
         ei->i_state &= ~EXT4_STATE_NEW;
 
+        ext4_update_inode_fsync_trans(handle, inode, 0);
 out_brelse:
         brelse(bh);
         ext4_std_error(inode->i_sb, err);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 8ab0c9518473..2b13dcfcf775 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -706,6 +706,8 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
         spin_lock_init(&(ei->i_block_reservation_lock));
         INIT_LIST_HEAD(&ei->i_aio_dio_complete_list);
         ei->cur_aio_dio = NULL;
+        ei->i_sync_tid = 0;
+        ei->i_datasync_tid = 0;
 
         return &ei->vfs_inode;
 }