[34-longterm 026/260] ext4: Make fsync sync new parent directories in no-journal mode

Paul Gortmaker
2011-01-02T07:21:43Z

From: Frank Mayhar <fmayhar@google.com>

commit 14ece1028b3ed53ffec1b1213ffc6acaf79ad77c upstream.

Add a new ext4 state to tell us when a file has been newly created; use
that state in ext4_sync_file in no-journal mode to tell us when we need
to sync the parent directory as well as the inode and data itself. This
fixes a problem in which a panic or power failure may lose the entire
file even when using fsync, since the parent directory entry is lost.

Addresses-Google-Bug: #2480057

Signed-off-by: Frank Mayhar <fmayhar@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
fs/ext4/ext4.h | 1 +
fs/ext4/fsync.c | 31 +++++++++++++++++++++++++++++--
fs/ext4/namei.c | 2 ++
3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 2e31640..650ef37 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1157,6 +1157,7 @@ enum {
EXT4_STATE_DA_ALLOC_CLOSE, /* Alloc DA blks on close */
EXT4_STATE_EXT_MIGRATE, /* Inode is migrating */
EXT4_STATE_DIO_UNWRITTEN, /* need convert on dio done*/
+ EXT4_STATE_NEWENTRY, /* File just added to dir */
};

#define EXT4_INODE_BIT_FNS(name, field) \
diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
index 42bd94a..6f25f9f 100644
--- a/fs/ext4/fsync.c
+++ b/fs/ext4/fsync.c
@@ -35,6 +35,29 @@
#include <trace/events/ext4.h>

/*
+ * If we're not journaling and this is a just-created file, we have to
+ * sync our parent directory (if it was freshly created) since
+ * otherwise it will only be written by writeback, leaving a huge
+ * window during which a crash may lose the file. This may apply for
+ * the parent directory's parent as well, and so on recursively, if
+ * they are also freshly created.
+ */
+static void ext4_sync_parent(struct inode *inode)
+{
+ struct dentry *dentry = NULL;
+
+ while (inode && ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
+ ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
+ dentry = list_entry(inode->i_dentry.next,
+ struct dentry, d_alias);
+ if (!dentry || !dentry->d_parent || !dentry->d_parent->d_inode)
+ break;
+ inode = dentry->d_parent->d_inode;
+ sync_mapping_buffers(inode->i_mapping);
+ }
+}
+
+/*
* akpm: A new design for ext4_sync_file().
*
* This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
@@ -67,8 +90,12 @@ int ext4_sync_file(struct file *file, struct dentry *dentry, int datasync)
if (ret < 0)
return ret;

- if (!journal)
- return simple_fsync(file, dentry, datasync);
+ if (!journal) {
+ ret = simple_fsync(file, dentry, datasync);
+ if (!ret && !list_empty(&inode->i_dentry))
+ ext4_sync_parent(inode);
+ return ret;
+ }

/*
* data=writeback,ordered:
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index efab592..2f31631 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1519,6 +1519,8 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
de->rec_len = ext4_rec_len_to_disk(blocksize, blocksize);
retval = add_dirent_to_buf(handle, dentry, inode, de, bh);
brelse(bh);
+ if (retval == 0)
+ ext4_set_inode_state(inode, EXT4_STATE_NEWENTRY);
return retval;
}

--
1.7.3.3