Re: [PATCH v4 01/15] fsnotify: annotate directory entry modification events

[Jan Kara <jack@suse.cz>]

On Sun 02-12-18 13:38:12, Amir Goldstein wrote:
> "dirent" events are referring to events that modify directory entries,
> such as create,delete,rename. Those events should always be reported
> on a watched directory, regardless if FS_EVENT_ON_CHILD is set
> on the watch mask.
> 
> fsnotify_nameremove() and fsnotify_move() were modified to no longer
> set the FS_EVENT_ON_CHILD event bit. This is a semantic change to
> align with the "dirent" event definition. It has no effect on any
> existing backend, because dnotify, inotify and audit always requets the
> child events and fanotify does not get the delete,rename events.
> 
> The fsnotify_dirent() helper is used instead of fsnotify_parent() to
> report a dirent event to dentry->d_parent without FS_EVENT_ON_CHILD
> and regardless if parent has the FS_EVENT_ON_CHILD bit set.
> 
> ALL_FSNOTIFY_DIRENT_EVENTS defines all the dirent event types and
> those event types have been extracted out of FS_EVENTS_POSS_ON_CHILD.
> 
> That means for a directory with an inotify watch and only dirent
> events in the mask (i.e. create,delete,move), all children dentries
> will no longer have the DCACHE_FSNOTIFY_PARENT_WATCHED flag set.
> This will allow all events that happen on children to be optimized
> away in __fsnotify_parent() without the need to dereference
> child->d_parent->d_inode->i_fsnotify_mask.
> 
> Since the dirent events are never repoted via __fsnotify_parent(),
> this results in no change of logic, but only an optimization.
> 
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  include/linux/fsnotify.h         | 42 +++++++++++++++++++++++++-------
>  include/linux/fsnotify_backend.h | 36 +++++++++++++++------------
>  2 files changed, 54 insertions(+), 24 deletions(-)
> 
> diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
> index 2ccb08cb5d6a..8de8f390cce2 100644
> --- a/include/linux/fsnotify.h
> +++ b/include/linux/fsnotify.h
> @@ -17,8 +17,35 @@
>  #include <linux/slab.h>
>  #include <linux/bug.h>
>  
> +/*
> + * Notify this @dir inode about a change in the directory entry @dentry.
> + *
> + * Unlike fsnotify_parent(), the event will be reported regardless of the
> + * FS_EVENT_ON_CHILD mask on the parent inode.
> + *
> + * When called with NULL @dir (from fsnotify_nameremove()), the dentry parent
> + * inode is used as the inode to report the event to.
> + */
> +static inline int fsnotify_dirent(struct inode *dir, struct dentry *dentry,
> +				  __u32 mask)
> +{
> +	if (!dir)
> +		dir = d_inode(dentry->d_parent);

Just a small nit: This !dir handling is only used for
fsnotify_nameremove(). So why not move that d_parent logic to that single
call site? That would make the function easier to argue about.

Otherwise I like the patch.

								Honza

> +
> +	/*
> +	 * This helper assumes d_parent and d_name are stable. It must be true
> +	 * when called from fsnotify_create()/fsnotify_mkdir(). Less sure about
> +	 * all callers that get here from d_delete() => fsnotify_nameremove().
> +	 */
> +	WARN_ON(!inode_is_locked(dir));
> +
> +	return fsnotify(dir, mask, d_inode(dentry), FSNOTIFY_EVENT_INODE,
> +			dentry->d_name.name, 0);
> +}
> +
>  /* Notify this dentry's parent about a child's events. */
> -static inline int fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask)
> +static inline int fsnotify_parent(const struct path *path,
> +				  struct dentry *dentry, __u32 mask)
>  {
>  	if (!dentry)
>  		dentry = path->dentry;
> @@ -85,8 +112,8 @@ static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
>  {
>  	struct inode *source = moved->d_inode;
>  	u32 fs_cookie = fsnotify_get_cookie();
> -	__u32 old_dir_mask = (FS_EVENT_ON_CHILD | FS_MOVED_FROM);
> -	__u32 new_dir_mask = (FS_EVENT_ON_CHILD | FS_MOVED_TO);
> +	__u32 old_dir_mask = FS_MOVED_FROM;
> +	__u32 new_dir_mask = FS_MOVED_TO;
>  	const unsigned char *new_name = moved->d_name.name;
>  
>  	if (old_dir == new_dir)
> @@ -136,7 +163,7 @@ static inline void fsnotify_nameremove(struct dentry *dentry, int isdir)
>  	if (isdir)
>  		mask |= FS_ISDIR;
>  
> -	fsnotify_parent(NULL, dentry, mask);
> +	fsnotify_dirent(NULL, dentry, mask);
>  }
>  
>  /*
> @@ -155,7 +182,7 @@ static inline void fsnotify_create(struct inode *inode, struct dentry *dentry)
>  {
>  	audit_inode_child(inode, dentry, AUDIT_TYPE_CHILD_CREATE);
>  
> -	fsnotify(inode, FS_CREATE, dentry->d_inode, FSNOTIFY_EVENT_INODE, dentry->d_name.name, 0);
> +	fsnotify_dirent(inode, dentry, FS_CREATE);
>  }
>  
>  /*
> @@ -176,12 +203,9 @@ static inline void fsnotify_link(struct inode *dir, struct inode *inode, struct
>   */
>  static inline void fsnotify_mkdir(struct inode *inode, struct dentry *dentry)
>  {
> -	__u32 mask = (FS_CREATE | FS_ISDIR);
> -	struct inode *d_inode = dentry->d_inode;
> -
>  	audit_inode_child(inode, dentry, AUDIT_TYPE_CHILD_CREATE);
>  
> -	fsnotify(inode, mask, d_inode, FSNOTIFY_EVENT_INODE, dentry->d_name.name, 0);
> +	fsnotify_dirent(inode, dentry, FS_CREATE | FS_ISDIR);
>  }
>  
>  /*
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index 7639774e7475..7f195d43efaf 100644
> --- a/include/linux/fsnotify_backend.h
> +++ b/include/linux/fsnotify_backend.h
> @@ -59,27 +59,33 @@
>   * dnotify and inotify. */
>  #define FS_EVENT_ON_CHILD	0x08000000
>  
> -/* This is a list of all events that may get sent to a parernt based on fs event
> - * happening to inodes inside that directory */
> -#define FS_EVENTS_POSS_ON_CHILD   (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
> -				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
> -				   FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
> -				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM | \
> -				   FS_OPEN_EXEC | FS_OPEN_EXEC_PERM)
> -
>  #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)
>  
> +/*
> + * Directory entry modification events - reported only to directory
> + * where entry is modified and not to a watching parent.
> + * The watching parent may get an FS_ATTRIB|FS_EVENT_ON_CHILD event
> + * when a directory entry inside a child subdir changes.
> + */
> +#define ALL_FSNOTIFY_DIRENT_EVENTS	(FS_CREATE | FS_DELETE | FS_MOVE)
> +
>  #define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM | \
>  				  FS_OPEN_EXEC_PERM)
>  
> +/*
> + * This is a list of all events that may get sent to a parent based on fs event
> + * happening to inodes inside that directory.
> + */
> +#define FS_EVENTS_POSS_ON_CHILD   (ALL_FSNOTIFY_PERM_EVENTS | \
> +				   FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
> +				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | \
> +				   FS_OPEN | FS_OPEN_EXEC)
> +
>  /* Events that can be reported to backends */
> -#define ALL_FSNOTIFY_EVENTS (FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
> -			     FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN | \
> -			     FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
> -			     FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
> -			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
> -			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME | \
> -			     FS_OPEN_EXEC | FS_OPEN_EXEC_PERM)
> +#define ALL_FSNOTIFY_EVENTS (ALL_FSNOTIFY_DIRENT_EVENTS | \
> +			     FS_EVENTS_POSS_ON_CHILD | \
> +			     FS_DELETE_SELF | FS_MOVE_SELF | FS_DN_RENAME | \
> +			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED)
>  
>  /* Extra flags that may be reported with event or control handling of events */
>  #define ALL_FSNOTIFY_FLAGS  (FS_EXCL_UNLINK | FS_ISDIR | FS_IN_ONESHOT | \
> -- 
> 2.17.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR