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 */