Re: [PATCH v4 2/2] ocfs2: snapshot the dentry name while tracing file release

[Joseph Qi]

On 10/22/26 5:08 PM, Cen Zhang wrote:
> ocfs2_file_release() passes the live dentry name and length to a trace
> event while holding oi->ip_lock. This lock protects the open count and
> delays RCU reclamation of external names, but it does not serialize name
> changes during rename. The dentry can switch between inline and external
> names, and a separately loaded length can describe a different name.
> 
> The ocfs2__file_ops event sizes and copies its __string separately.
> A concurrently rewritten inline name need not remain consistent between
> those operations. External names can also be selected at this call site;
> the existing spinlock critical section protects their allocation lifetime,
> while a snapshot additionally pairs a stable name with its length.
> 
> Take a name snapshot before acquiring oi->ip_lock and release it after
> dropping the lock. Keep the trace call and open-count argument inside
> the original critical section. Cache the event-enabled check so the
> snapshot stays paired even if tracing is toggled meanwhile.
> 
> Fixes: 468eedde23d6 ("ocfs2: Remove mlog(0) from fs/ocfs2/file.c")
> Cc: stable@xxxxxxxxxxxxxxx
> Assisted-by: LLM
> Signed-off-by: Cen Zhang <zzzccc427@xxxxxxxxx>

Reviewed-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>

> ---
>  fs/ocfs2/file.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> index c6e7606ff9e1..b3a37b9d259a 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -141,18 +141,26 @@ leave:
>  static int ocfs2_file_release(struct inode *inode, struct file *file)
>  {
>  	struct ocfs2_inode_info *oi = OCFS2_I(inode);
> +	struct dentry *dentry = file->f_path.dentry;
> +	struct name_snapshot name;
> +	bool trace_enabled = trace_ocfs2_file_release_enabled();
> +
> +	if (trace_enabled)
> +		take_dentry_name_snapshot(&name, dentry);
>  
>  	spin_lock(&oi->ip_lock);
>  	if (!--oi->ip_open_count)
>  		oi->ip_flags &= ~OCFS2_INODE_OPEN_DIRECT;
>  
> -	trace_ocfs2_file_release(inode, file, file->f_path.dentry,
> -				 oi->ip_blkno,
> -				 file->f_path.dentry->d_name.len,
> -				 file->f_path.dentry->d_name.name,
> -				 oi->ip_open_count);
> +	if (trace_enabled)
> +		trace_ocfs2_file_release(inode, file, dentry,
> +					 oi->ip_blkno, name.name.len,
> +					 name.name.name, oi->ip_open_count);
>  	spin_unlock(&oi->ip_lock);
>  
> +	if (trace_enabled)
> +		release_dentry_name_snapshot(&name);
> +
>  	ocfs2_free_file_private(inode, file);
>  
>  	return 0;