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    Subject[PATCH 05/13] fsnotify: parent event notification
    Date
    inotify and dnotify both use a similar parent notification mechanism.  We
    add a generic parent notification mechanism to fsnotify for both of these
    to use. This new machanism also adds the dentry flag optimization which
    exists for inotify to dnotify.

    Signed-off-by: Eric Paris <eparis@redhat.com>
    ---

    fs/notify/inode_mark.c | 48 +++++++++++++++++++++++++++++++++
    include/linux/dcache.h | 3 +-
    include/linux/fsnotify.h | 56 ++++++++++++++++++++++++++++++++++++--
    include/linux/fsnotify_backend.h | 43 +++++++++++++++++++++++++++++
    4 files changed, 146 insertions(+), 4 deletions(-)

    diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
    index facd561..144b09a 100644
    --- a/fs/notify/inode_mark.c
    +++ b/fs/notify/inode_mark.c
    @@ -41,6 +41,48 @@ void fsnotify_put_mark(struct fsnotify_mark_entry *entry)
    }

    /*
    + * Given an inode, first check if we care what happens to out children. Inotify
    + * and dnotify both tell their parents about events. If we care about any event
    + * on a child we run all of our children and set a dentry flag saying that the
    + * parent cares. Thus when an event happens on a child it can quickly tell if
    + * if there is a need to find a parent and send the event to the parent.
    + */
    +static inline void fsnotify_update_dentry_child_flags(struct inode *inode)
    +{
    + struct dentry *alias;
    + int watched;
    +
    + if (!S_ISDIR(inode->i_mode))
    + return;
    +
    + /* determine if the children should tell inode about their events */
    + watched = fsnotify_inode_watches_children(inode);
    +
    + spin_lock(&dcache_lock);
    + /* run all of the dentries associated with this inode. Since this is a
    + * directory, there damn well better only be one item on this list */
    + list_for_each_entry(alias, &inode->i_dentry, d_alias) {
    + struct dentry *child;
    +
    + /* run all of the children of the original inode and fix their
    + * d_flags to indicate parental interest (their parent is the
    + * original inode) */
    + list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
    + if (!child->d_inode)
    + continue;
    +
    + spin_lock(&child->d_lock);
    + if (watched)
    + child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
    + else
    + child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
    + spin_unlock(&child->d_lock);
    + }
    + }
    + spin_unlock(&dcache_lock);
    +}
    +
    +/*
    * recalculate the mask of events relevant to a given inode locked.
    */
    static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
    @@ -65,6 +107,8 @@ void fsnotify_recalc_inode_mask(struct inode *inode)
    spin_lock(&inode->i_lock);
    fsnotify_recalc_inode_mask_locked(inode);
    spin_unlock(&inode->i_lock);
    +
    + fsnotify_update_dentry_child_flags(inode);
    }

    /*
    @@ -113,6 +157,8 @@ void fsnotify_destroy_mark_by_entry(struct fsnotify_mark_entry *entry)
    spin_unlock(&entry->lock);

    group->ops->freeing_mark(entry, group);
    +
    + fsnotify_update_dentry_child_flags(inode);
    }

    void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
    @@ -218,6 +264,8 @@ int fsnotify_add_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *
    if (lentry) {
    ret = -EEXIST;
    fsnotify_put_mark(lentry);
    + } else {
    + fsnotify_update_dentry_child_flags(inode);
    }

    return ret;
    diff --git a/include/linux/dcache.h b/include/linux/dcache.h
    index c66d224..2b935f2 100644
    --- a/include/linux/dcache.h
    +++ b/include/linux/dcache.h
    @@ -180,7 +180,8 @@ d_iput: no no no yes
    #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
    #define DCACHE_UNHASHED 0x0010

    -#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched */
    +#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched by inotify */
    +#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0040 /* Parent inode is watched by some fsnotify listener */

    #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */

    diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
    index 4e04ab2..7b45f29 100644
    --- a/include/linux/fsnotify.h
    +++ b/include/linux/fsnotify.h
    @@ -20,10 +20,43 @@
    * fsnotify_d_instantiate - instantiate a dentry for inode
    * Called with dcache_lock held.
    */
    -static inline void fsnotify_d_instantiate(struct dentry *entry,
    - struct inode *inode)
    +static inline void fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
    {
    - inotify_d_instantiate(entry, inode);
    + __fsnotify_d_instantiate(dentry, inode);
    +
    + /* call the legacy inotify shit */
    + inotify_d_instantiate(dentry, inode);
    +}
    +
    +/* Notify this dentry's parent about a child's events. */
    +static inline void fsnotify_parent(struct dentry *dentry, __u32 mask)
    +{
    + struct dentry *parent;
    + struct inode *p_inode;
    + char send = 0;
    +
    + if (!(dentry->d_flags | DCACHE_FSNOTIFY_PARENT_WATCHED))
    + return;
    +
    + /* we are notifying a parent so come up with the new mask which
    + * specifies these are events which came from a child. */
    + mask |= FS_EVENT_ON_CHILD;
    +
    + spin_lock(&dentry->d_lock);
    + parent = dentry->d_parent;
    + p_inode = parent->d_inode;
    +
    + if (p_inode->i_fsnotify_mask & mask) {
    + dget(parent);
    + send = 1;
    + }
    +
    + spin_unlock(&dentry->d_lock);
    +
    + if (send) {
    + fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE);
    + dput(parent);
    + }
    }

    /*
    @@ -32,6 +65,14 @@ static inline void fsnotify_d_instantiate(struct dentry *entry,
    */
    static inline void fsnotify_d_move(struct dentry *entry)
    {
    + struct dentry *parent;
    +
    + parent = entry->d_parent;
    + if (fsnotify_inode_watches_children(parent->d_inode))
    + entry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
    + else
    + entry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
    +
    inotify_d_move(entry);
    }

    @@ -113,6 +154,8 @@ static inline void fsnotify_nameremove(struct dentry *dentry, int isdir)
    isdir = FS_IN_ISDIR;
    dnotify_parent(dentry, DN_DELETE);
    inotify_dentry_parent_queue_event(dentry, IN_DELETE|isdir, 0, dentry->d_name.name);
    +
    + fsnotify_parent(dentry, FS_DELETE|isdir);
    }

    /*
    @@ -182,6 +225,7 @@ static inline void fsnotify_access(struct dentry *dentry)
    inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
    inotify_inode_queue_event(inode, mask, 0, NULL, NULL);

    + fsnotify_parent(dentry, mask);
    fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
    }

    @@ -200,6 +244,7 @@ static inline void fsnotify_modify(struct dentry *dentry)
    inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
    inotify_inode_queue_event(inode, mask, 0, NULL, NULL);

    + fsnotify_parent(dentry, mask);
    fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
    }

    @@ -217,6 +262,7 @@ static inline void fsnotify_open(struct dentry *dentry)
    inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
    inotify_inode_queue_event(inode, mask, 0, NULL, NULL);

    + fsnotify_parent(dentry, mask);
    fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
    }

    @@ -237,6 +283,7 @@ static inline void fsnotify_close(struct file *file)
    inotify_dentry_parent_queue_event(dentry, mask, 0, name);
    inotify_inode_queue_event(inode, mask, 0, NULL, NULL);

    + fsnotify_parent(dentry, mask);
    fsnotify(inode, mask, file, FSNOTIFY_EVENT_FILE);
    }

    @@ -254,6 +301,7 @@ static inline void fsnotify_xattr(struct dentry *dentry)
    inotify_dentry_parent_queue_event(dentry, mask, 0, dentry->d_name.name);
    inotify_inode_queue_event(inode, mask, 0, NULL, NULL);

    + fsnotify_parent(dentry, mask);
    fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE);
    }

    @@ -304,6 +352,8 @@ static inline void fsnotify_change(struct dentry *dentry, unsigned int ia_valid)
    inotify_inode_queue_event(inode, in_mask, 0, NULL, NULL);
    inotify_dentry_parent_queue_event(dentry, in_mask, 0,
    dentry->d_name.name);
    +
    + fsnotify_parent(dentry, in_mask);
    fsnotify(inode, in_mask, inode, FSNOTIFY_EVENT_INODE);
    }
    }
    diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
    index 605c79e..aa8a3ea 100644
    --- a/include/linux/fsnotify_backend.h
    +++ b/include/linux/fsnotify_backend.h
    @@ -45,8 +45,17 @@
    #define FS_DN_RENAME 0x10000000ul /* file renamed */
    #define FS_DN_MULTISHOT 0x20000000ul /* dnotify multishot */

    +/* this inode cares about things that happen to it's children. Always set for
    + * dnotify and inotify. never set for fanotify */
    #define FS_EVENT_ON_CHILD 0x08000000ul

    +/* 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)
    +
    struct fsnotify_group;
    struct fsnotify_event;
    struct fsnotify_mark_entry;
    @@ -151,6 +160,37 @@ struct fsnotify_mark_entry {
    extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is);
    extern void __fsnotify_inode_delete(struct inode *inode);

    +static inline int fsnotify_inode_watches_children(struct inode *inode)
    +{
    + /* FS_EVENT_ON_CHILD is set if the inode may care */
    + if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
    + return 0;
    + /* this inode might care about child events, does it care about the
    + * specific set of events that can happen on a child? */
    + return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
    +}
    +
    +/*
    + * fsnotify_d_instantiate - instantiate a dentry for inode
    + * Called with dcache_lock held.
    + */
    +static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
    +{
    + struct dentry *parent;
    + struct inode *p_inode;
    +
    + if (!inode)
    + return;
    +
    + spin_lock(&dentry->d_lock);
    + parent = dentry->d_parent;
    + p_inode = parent->d_inode;
    +
    + if (fsnotify_inode_watches_children(p_inode))
    + dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
    + spin_unlock(&dentry->d_lock);
    +}
    +
    /* called from fsnotify interfaces, such as fanotify or dnotify */
    extern void fsnotify_recalc_global_mask(void);
    extern void fsnotify_recalc_group_mask(struct fsnotify_group *group);
    @@ -182,6 +222,9 @@ static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int d
    static inline void __fsnotify_inode_delete(struct inode *inode)
    {}

    +static inline void __fsnotify_d_instantiate(struct dentry *dentry, struct inode *inode)
    +{}
    +
    #endif /* CONFIG_FSNOTIFY */

    #endif /* __KERNEL __ */


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