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Subjectext4: call blkdev_issue_flush on fsync
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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>
---

--- linux-2.6.29-rc1-orig/fs/ext4/fsync.c 2008-12-25 08:26:37.000000000 +0900
+++ linux-2.6.29-rc1/fs/ext4/fsync.c 2009-01-16 22:18:51.000000000 +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 +77,33 @@ int ext4_sync_file(struct file *file, st
*/
if (ext4_should_journal_data(inode)) {
ret = ext4_force_commit(inode->i_sb);
+ if (!(journal->j_flags & JBD2_BARRIER))
+ goto no_journal_barrier;
goto out;
}

- if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
- goto out;
+ if (datasync && !(i_state & I_DIRTY_DATASYNC))
+ goto flush_blkdev;

/*
* 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 (journal && !(journal->j_flags & JBD2_BARRIER))
+ goto no_journal_barrier;
}
+
+flush_blkdev:
+ if (!(i_state & I_DIRTY_PAGES))
+ goto out;
+no_journal_barrier:
+ blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
out:
return ret;
}



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