[PATCH 3/7] ext4: call blkdev_issue_flush() on fsync()

Fernando Luis Vázquez Cao
2009-03-30T12:15:22Z

To ensure that bits are truly on-disk after an fsync or fdatasync, we
should force a disk flush explicitly when there is dirty data/metadata
and the journal didn't emit a write barrier (either because metadata is
not being synched or barriers are disabled).

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
---

diff -urNp linux-2.6.29-orig/fs/ext4/fsync.c linux-2.6.29/fs/ext4/fsync.c
--- linux-2.6.29-orig/fs/ext4/fsync.c 2009-03-24 08:12:14.000000000 +0900
+++ linux-2.6.29/fs/ext4/fsync.c 2009-03-30 15:35:26.000000000 +0900
@@ -48,6 +48,7 @@ int ext4_sync_file(struct file *file, st
{
struct inode *inode = dentry->d_inode;
journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
+ unsigned long i_state = inode->i_state;
int ret = 0;

J_ASSERT(ext4_journal_current_handle() == NULL);
@@ -76,25 +77,30 @@ int ext4_sync_file(struct file *file, st
*/
if (ext4_should_journal_data(inode)) {
ret = ext4_force_commit(inode->i_sb);
- goto out;
+ if (!ret && !(journal->j_flags & JBD2_BARRIER))
+ ret = block_flush_device(inode->i_sb->s_bdev);
+ return ret;
}

- if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
- goto out;
+ if (datasync && !(i_state & I_DIRTY_DATASYNC)) {
+ if (i_state & I_DIRTY_PAGES)
+ ret = block_flush_device(inode->i_sb->s_bdev);
+ return ret;
+ }

/*
* 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)) {
+ if (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 (journal && (journal->j_flags & JBD2_BARRIER))
- blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
+ if (!ret && journal && !(journal->j_flags & JBD2_BARRIER))
+ ret = block_flush_device(inode->i_sb->s_bdev);
}
-out:
+
return ret;
}