[PATCH 3/4] ext3: Add replace-on-truncate hueristics for data=writeback mode

Theodore Ts'o
2009-04-03T07:01:11Z

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>
---
fs/ext3/file.c | 4 ++++
fs/ext3/inode.c | 3 +++
include/linux/ext3_fs.h | 1 +
3 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/fs/ext3/file.c b/fs/ext3/file.c
index 3be1e06..4a04cbb 100644
--- a/fs/ext3/file.c
+++ b/fs/ext3/file.c
@@ -33,6 +33,10 @@
*/
static int ext3_release_file (struct inode * inode, struct file * filp)
{
+ if (EXT3_I(inode)->i_state & EXT3_STATE_FLUSH_ON_CLOSE) {
+ filemap_flush(inode->i_mapping);
+ EXT3_I(inode)->i_state &= ~EXT3_STATE_FLUSH_ON_CLOSE;
+ }
/* if we are the last writer on the inode, drop the block reservation */
if ((filp->f_mode & FMODE_WRITE) &&
(atomic_read(&inode->i_writecount) == 1))
diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 5fa453b..0f5bca0 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().
diff --git a/include/linux/ext3_fs.h b/include/linux/ext3_fs.h
index dd495b8..d2630c5 100644
--- a/include/linux/ext3_fs.h
+++ b/include/linux/ext3_fs.h
@@ -208,6 +208,7 @@ static inline __u32 ext3_mask_flags(umode_t mode, __u32 flags)
#define EXT3_STATE_JDATA 0x00000001 /* journaled data exists */
#define EXT3_STATE_NEW 0x00000002 /* inode is newly created */
#define EXT3_STATE_XATTR 0x00000004 /* has in-inode xattrs */
+#define EXT3_STATE_FLUSH_ON_CLOSE 0x00000008

/* Used to pass group descriptor data when online resize is done */
struct ext3_new_group_input {
--
1.5.6.3