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fsnotify: parent event notification

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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>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Eric Paris
2009-05-21 17:01:29 -04:00
parent 3be25f49b9
commit c28f7e56e9
6 changed files with 205 additions and 10 deletions
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91
fs/notify/fsnotify.c
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@@ -34,6 +34,97 @@ void __fsnotify_inode_delete(struct inode *inode)
}
EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
/*
* Given an inode, first check if we care what happens to our 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.
*/
void __fsnotify_update_child_dentry_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);
}
/* Notify this dentry's parent about a child's events. */
void __fsnotify_parent(struct dentry *dentry, __u32 mask)
{
struct dentry *parent;
struct inode *p_inode;
bool send = false;
bool should_update_children = false;
if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
return;
spin_lock(&dentry->d_lock);
parent = dentry->d_parent;
p_inode = parent->d_inode;
if (fsnotify_inode_watches_children(p_inode)) {
if (p_inode->i_fsnotify_mask & mask) {
dget(parent);
send = true;
}
} else {
/*
* The parent doesn't care about events on it's children but
* at least one child thought it did. We need to run all the
* children and update their d_flags to let them know p_inode
* doesn't care about them any more.
*/
dget(parent);
should_update_children = true;
}
spin_unlock(&dentry->d_lock);
if (send) {
/* 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;
fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE);
dput(parent);
}
if (unlikely(should_update_children)) {
__fsnotify_update_child_dentry_flags(p_inode);
dput(parent);
}
}
EXPORT_SYMBOL_GPL(__fsnotify_parent);
/*
* This is the main call to fsnotify. The VFS calls into hook specific functions
* in linux/fsnotify.h. Those functions then in turn call here. Here will call