ext3: Add replace-on-truncate hueristics for data=writeback mode

In data=writeback mode, start an asynchronous flush when closing a
file which had been previously truncated down to zero.  This lowers
the probability of data loss in the case of applications that attempt
to replace a file using truncate.

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

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 5fa453b49a64..0f5bca0d82fc 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -2346,6 +2346,9 @@ void ext3_truncate(struct inode *inode)
         if (!ext3_can_truncate(inode))
                 return;
 
+        if (inode->i_size == 0 && ext3_should_writeback_data(inode))
+                ei->i_state |= EXT3_STATE_FLUSH_ON_CLOSE;
+
         /*
          * We have to lock the EOF page here, because lock_page() nests
          * outside journal_start().