1 files changed, 177 insertions, 0 deletions
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
new file mode 100644
index 000000000000..1a55718b38aa
--- /dev/null
+++ b/include/linux/fsnotify_backend.h
@@ -0,0 +1,177 @@
+/*
+ * Filesystem access notification for Linux
+ *
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
+ */
+
+#ifndef __LINUX_FSNOTIFY_BACKEND_H
+#define __LINUX_FSNOTIFY_BACKEND_H
+
+#ifdef __KERNEL__
+
+#include <linux/fs.h> /* struct inode */
+#include <linux/list.h>
+#include <linux/path.h> /* struct path */
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+#include <asm/atomic.h>
+
+/*
+ * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
+ * convert between them.  dnotify only needs conversion at watch creation
+ * so no perf loss there.  fanotify isn't defined yet, so it can use the
+ * wholes if it needs more events.
+ */
+#define FS_ACCESS		0x00000001	/* File was accessed */
+#define FS_MODIFY		0x00000002	/* File was modified */
+#define FS_ATTRIB		0x00000004	/* Metadata changed */
+#define FS_CLOSE_WRITE		0x00000008	/* Writtable file was closed */
+#define FS_CLOSE_NOWRITE	0x00000010	/* Unwrittable file closed */
+#define FS_OPEN			0x00000020	/* File was opened */
+#define FS_MOVED_FROM		0x00000040	/* File was moved from X */
+#define FS_MOVED_TO		0x00000080	/* File was moved to Y */
+#define FS_CREATE		0x00000100	/* Subfile was created */
+#define FS_DELETE		0x00000200	/* Subfile was deleted */
+#define FS_DELETE_SELF		0x00000400	/* Self was deleted */
+#define FS_MOVE_SELF		0x00000800	/* Self was moved */
+
+#define FS_UNMOUNT		0x00002000	/* inode on umount fs */
+#define FS_Q_OVERFLOW		0x00004000	/* Event queued overflowed */
+#define FS_IN_IGNORED		0x00008000	/* last inotify event here */
+
+#define FS_IN_ISDIR		0x40000000	/* event occurred against dir */
+#define FS_IN_ONESHOT		0x80000000	/* only send event once */
+
+#define FS_DN_RENAME		0x10000000	/* file renamed */
+#define FS_DN_MULTISHOT		0x20000000	/* dnotify multishot */
+
+struct fsnotify_group;
+struct fsnotify_event;
+
+/*
+ * Each group much define these ops.  The fsnotify infrastructure will call
+ * these operations for each relevant group.
+ *
+ * handle_event - main call for a group to handle an fs event
+ * free_group_priv - called when a group refcnt hits 0 to clean up the private union
+ */
+struct fsnotify_ops {
+	int (*handle_event)(struct fsnotify_group *group, struct fsnotify_event *event);
+	void (*free_group_priv)(struct fsnotify_group *group);
+};
+
+/*
+ * A group is a "thing" that wants to receive notification about filesystem
+ * events.  The mask holds the subset of event types this group cares about.
+ * refcnt on a group is up to the implementor and at any moment if it goes 0
+ * everything will be cleaned up.
+ */
+struct fsnotify_group {
+	/*
+	 * global list of all groups receiving events from fsnotify.
+	 * anchored by fsnotify_groups and protected by either fsnotify_grp_mutex
+	 * or fsnotify_grp_srcu depending on write vs read.
+	 */
+	struct list_head group_list;
+
+	/*
+	 * Defines all of the event types in which this group is interested.
+	 * This mask is a bitwise OR of the FS_* events from above.  Each time
+	 * this mask changes for a group (if it changes) the correct functions
+	 * must be called to update the global structures which indicate global
+	 * interest in event types.
+	 */
+	__u32 mask;
+
+	/*
+	 * How the refcnt is used is up to each group.  When the refcnt hits 0
+	 * fsnotify will clean up all of the resources associated with this group.
+	 * As an example, the dnotify group will always have a refcnt=1 and that
+	 * will never change.  Inotify, on the other hand, has a group per
+	 * inotify_init() and the refcnt will hit 0 only when that fd has been
+	 * closed.
+	 */
+	atomic_t refcnt;		/* things with interest in this group */
+	unsigned int group_num;		/* simply prevents accidental group collision */
+
+	const struct fsnotify_ops *ops;	/* how this group handles things */
+
+	/* prevents double list_del of group_list.  protected by global fsnotify_gr_mutex */
+	bool on_group_list;
+
+	/* groups can define private fields here or use the void *private */
+	union {
+		void *private;
+	};
+};
+
+/*
+ * all of the information about the original object we want to now send to
+ * a group.  If you want to carry more info from the accessing task to the
+ * listener this structure is where you need to be adding fields.
+ */
+struct fsnotify_event {
+	spinlock_t lock;	/* protection for the associated event_holder and private_list */
+	/* to_tell may ONLY be dereferenced during handle_event(). */
+	struct inode *to_tell;	/* either the inode the event happened to or its parent */
+	/*
+	 * depending on the event type we should have either a path or inode
+	 * We hold a reference on path, but NOT on inode.  Since we have the ref on
+	 * the path, it may be dereferenced at any point during this object's
+	 * lifetime.  That reference is dropped when this object's refcnt hits
+	 * 0.  If this event contains an inode instead of a path, the inode may
+	 * ONLY be used during handle_event().
+	 */
+	union {
+		struct path path;
+		struct inode *inode;
+	};
+/* when calling fsnotify tell it if the data is a path or inode */
+#define FSNOTIFY_EVENT_NONE	0
+#define FSNOTIFY_EVENT_PATH	1
+#define FSNOTIFY_EVENT_INODE	2
+#define FSNOTIFY_EVENT_FILE	3
+	int data_type;		/* which of the above union we have */
+	atomic_t refcnt;	/* how many groups still are using/need to send this event */
+	__u32 mask;		/* the type of access, bitwise OR for FS_* event types */
+};
+
+#ifdef CONFIG_FSNOTIFY
+
+/* called from the vfs helpers */
+
+/* main fsnotify call to send events */
+extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is);
+
+
+/* called from fsnotify listeners, such as fanotify or dnotify */
+
+/* must call when a group changes its ->mask */
+extern void fsnotify_recalc_global_mask(void);
+/* get a reference to an existing or create a new group */
+extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num,
+						    __u32 mask,
+						    const struct fsnotify_ops *ops);
+/* drop reference on a group from fsnotify_obtain_group */
+extern void fsnotify_put_group(struct fsnotify_group *group);
+
+/* take a reference to an event */
+extern void fsnotify_get_event(struct fsnotify_event *event);
+extern void fsnotify_put_event(struct fsnotify_event *event);
+/* find private data previously attached to an event */
+extern struct fsnotify_event_private_data *fsnotify_get_priv_from_event(struct fsnotify_group *group,
+									struct fsnotify_event *event);
+
+/* put here because inotify does some weird stuff when destroying watches */
+extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
+						    void *data, int data_is);
+#else
+
+static inline void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is)
+{}
+#endif	/* CONFIG_FSNOTIFY */
+
+#endif	/* __KERNEL __ */
+
+#endif	/* __LINUX_FSNOTIFY_BACKEND_H */