Re: [PATCH v2 07/28] fsnotify: add FSNOTIFY_EVENT_RENAME data type

[Jeff Layton <jlayton@kernel.org>]

On Thu, 2026-04-16 at 21:24 +0200, Amir Goldstein wrote:
> On Thu, Apr 16, 2026 at 7:35 PM Jeff Layton <jlayton@kernel.org> wrote:
> > 
> > Add a new fsnotify_rename_data struct and FSNOTIFY_EVENT_RENAME data
> > type that carries both the moved dentry and the inode that was
> > overwritten by the rename (if any).
> > 
> > Update fsnotify_data_inode(), fsnotify_data_dentry(), and
> > fsnotify_data_sb() to handle the new type, and add a new
> > fsnotify_data_rename_target() helper for extracting the overwritten
> > target inode.
> > 
> > Update fsnotify_move() to use the new data type for FS_RENAME and
> > FS_MOVED_TO events, passing the overwritten target inode through the
> > event data. FS_MOVED_FROM is unchanged since the source directory
> > doesn't need overwrite information.
> > 
> > This is done so that fsnotify consumers like nfsd can atomically
> > observe the overwritten file when a rename replaces an existing entry,
> > without needing a separate FS_DELETE event.
> > 
> > Assisted-by: Claude (Anthropic Claude Code)
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> >  include/linux/fsnotify.h         |  8 ++++++--
> >  include/linux/fsnotify_backend.h | 20 ++++++++++++++++++++
> >  2 files changed, 26 insertions(+), 2 deletions(-)
> 
> It is strange to me that the NFS protocol needs to report the overwritten
> node in the same event of the rename, but oh well, fine by me.
> 

Yeah, it's not very useful, but the protocol requires it. Unfortunately
RFC5661 was written before anyone had made a real implementation of
directory delegations. If we were rewriting it today, we'd probably
make that info optional.

> Feel free to add:
> Reviewed-by: Amir Goldstein <amir73il@gmail.com>
> 
> 

Thanks, Amir!

> > 
> > diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
> > index 079c18bcdbde..bda798bc67bc 100644
> > --- a/include/linux/fsnotify.h
> > +++ b/include/linux/fsnotify.h
> > @@ -257,6 +257,10 @@ static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
> >         __u32 new_dir_mask = FS_MOVED_TO;
> >         __u32 rename_mask = FS_RENAME;
> >         const struct qstr *new_name = &moved->d_name;
> > +       struct fsnotify_rename_data rd = {
> > +               .moved = moved,
> > +               .target = target,
> > +       };
> > 
> >         if (isdir) {
> >                 old_dir_mask |= FS_ISDIR;
> > @@ -265,12 +269,12 @@ static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
> >         }
> > 
> >         /* Event with information about both old and new parent+name */
> > -       fsnotify_name(rename_mask, moved, FSNOTIFY_EVENT_DENTRY,
> > +       fsnotify_name(rename_mask, &rd, FSNOTIFY_EVENT_RENAME,
> >                       old_dir, old_name, 0);
> > 
> >         fsnotify_name(old_dir_mask, source, FSNOTIFY_EVENT_INODE,
> >                       old_dir, old_name, fs_cookie);
> > -       fsnotify_name(new_dir_mask, source, FSNOTIFY_EVENT_INODE,
> > +       fsnotify_name(new_dir_mask, &rd, FSNOTIFY_EVENT_RENAME,
> >                       new_dir, new_name, fs_cookie);
> > 
> >         if (target)
> > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> > index 66e185bd1b1b..f8c8fb7f34ae 100644
> > --- a/include/linux/fsnotify_backend.h
> > +++ b/include/linux/fsnotify_backend.h
> > @@ -311,6 +311,7 @@ enum fsnotify_data_type {
> >         FSNOTIFY_EVENT_DENTRY,
> >         FSNOTIFY_EVENT_MNT,
> >         FSNOTIFY_EVENT_ERROR,
> > +       FSNOTIFY_EVENT_RENAME,
> >  };
> > 
> >  struct fs_error_report {
> > @@ -335,6 +336,11 @@ struct fsnotify_mnt {
> >         u64 mnt_id;
> >  };
> > 
> > +struct fsnotify_rename_data {
> > +       struct dentry *moved;   /* the dentry that was renamed */
> > +       struct inode *target;   /* inode overwritten by rename, or NULL */
> > +};
> > +
> >  static inline struct inode *fsnotify_data_inode(const void *data, int data_type)
> >  {
> >         switch (data_type) {
> > @@ -348,6 +354,8 @@ static inline struct inode *fsnotify_data_inode(const void *data, int data_type)
> >                 return d_inode(file_range_path(data)->dentry);
> >         case FSNOTIFY_EVENT_ERROR:
> >                 return ((struct fs_error_report *)data)->inode;
> > +       case FSNOTIFY_EVENT_RENAME:
> > +               return d_inode(((const struct fsnotify_rename_data *)data)->moved);
> >         default:
> >                 return NULL;
> >         }
> > @@ -363,6 +371,8 @@ static inline struct dentry *fsnotify_data_dentry(const void *data, int data_typ
> >                 return ((const struct path *)data)->dentry;
> >         case FSNOTIFY_EVENT_FILE_RANGE:
> >                 return file_range_path(data)->dentry;
> > +       case FSNOTIFY_EVENT_RENAME:
> > +               return ((struct fsnotify_rename_data *)data)->moved;
> >         default:
> >                 return NULL;
> >         }
> > @@ -395,6 +405,8 @@ static inline struct super_block *fsnotify_data_sb(const void *data,
> >                 return file_range_path(data)->dentry->d_sb;
> >         case FSNOTIFY_EVENT_ERROR:
> >                 return ((struct fs_error_report *) data)->sb;
> > +       case FSNOTIFY_EVENT_RENAME:
> > +               return ((const struct fsnotify_rename_data *)data)->moved->d_sb;
> >         default:
> >                 return NULL;
> >         }
> > @@ -430,6 +442,14 @@ static inline struct fs_error_report *fsnotify_data_error_report(
> >         }
> >  }
> > 
> > +static inline struct inode *fsnotify_data_rename_target(const void *data,
> > +                                                       int data_type)
> > +{
> > +       if (data_type == FSNOTIFY_EVENT_RENAME)
> > +               return ((const struct fsnotify_rename_data *)data)->target;
> > +       return NULL;
> > +}
> > +
> >  static inline const struct file_range *fsnotify_data_file_range(
> >                                                         const void *data,
> >                                                         int data_type)
> > 
> > --
> > 2.53.0
> > 

-- 
Jeff Layton <jlayton@kernel.org>