/* SPDX-License-Identifier: GPL-2.0 */
/*
 * 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/idr.h> /* inotify uses this */
#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 <linux/atomic.h>
#include <linux/user_namespace.h>
#include <linux/refcount.h>
#include <linux/mempool.h>
#include <linux/sched/mm.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      /* Writable file was closed */
#define FS_CLOSE_NOWRITE        0x00000010      /* Unwritable 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_OPEN_EXEC            0x00001000      /* File was opened for exec */

#define FS_UNMOUNT              0x00002000      /* inode on umount fs */
#define FS_Q_OVERFLOW           0x00004000      /* Event queued overflowed */
#define FS_ERROR                0x00008000      /* Filesystem Error (fanotify) */

/*
 * FS_IN_IGNORED overloads FS_ERROR.  It is only used internally by inotify
 * which does not support FS_ERROR.
 */
#define FS_IN_IGNORED           0x00008000      /* last inotify event here */

#define FS_OPEN_PERM            0x00010000      /* open event in an permission hook */
#define FS_ACCESS_PERM          0x00020000      /* access event in a permissions hook */
#define FS_OPEN_EXEC_PERM       0x00040000      /* open/exec event in a permission hook */
/* #define FS_DIR_MODIFY        0x00080000 */   /* Deprecated (reserved) */

#define FS_PRE_ACCESS           0x00100000      /* Pre-content access hook */

#define FS_MNT_ATTACH           0x01000000      /* Mount was attached */
#define FS_MNT_DETACH           0x02000000      /* Mount was detached */
#define FS_MNT_MOVE             (FS_MNT_ATTACH | FS_MNT_DETACH)

/*
 * Set on inode mark that cares about things that happen to its children.
 * Always set for dnotify and inotify.
 * Set on inode/sb/mount marks that care about parent/name info.
 */
#define FS_EVENT_ON_CHILD       0x08000000

#define FS_RENAME               0x10000000      /* File was renamed */
#define FS_DN_MULTISHOT         0x20000000      /* dnotify multishot */
#define FS_ISDIR                0x40000000      /* event occurred against dir */

#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 | FS_RENAME)

/* Mount namespace events */
#define FSNOTIFY_MNT_EVENTS (FS_MNT_ATTACH | FS_MNT_DETACH)

/* Content events can be used to inspect file content */
#define FSNOTIFY_CONTENT_PERM_EVENTS (FS_OPEN_PERM | FS_OPEN_EXEC_PERM | \
                                      FS_ACCESS_PERM)
/* Pre-content events can be used to fill file content */
#define FSNOTIFY_PRE_CONTENT_EVENTS  (FS_PRE_ACCESS)

#define ALL_FSNOTIFY_PERM_EVENTS (FSNOTIFY_CONTENT_PERM_EVENTS | \
                                  FSNOTIFY_PRE_CONTENT_EVENTS)

/*
 * This is a list of all events that may get sent to a parent that is watching
 * with flag FS_EVENT_ON_CHILD based on fs event on a child of 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)

/*
 * This is a list of all events that may get sent with the parent inode as the
 * @to_tell argument of fsnotify().
 * It may include events that can be sent to an inode/sb/mount mark, but cannot
 * be sent to a parent watching children.
 */
#define FS_EVENTS_POSS_TO_PARENT (FS_EVENTS_POSS_ON_CHILD)

/* Events that can be reported to backends */
#define ALL_FSNOTIFY_EVENTS (ALL_FSNOTIFY_DIRENT_EVENTS | \
                             FSNOTIFY_MNT_EVENTS | \
                             FS_EVENTS_POSS_ON_CHILD | \
                             FS_DELETE_SELF | FS_MOVE_SELF | \
                             FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
                             FS_ERROR)

/* Extra flags that may be reported with event or control handling of events */
#define ALL_FSNOTIFY_FLAGS  (FS_ISDIR | FS_EVENT_ON_CHILD | FS_DN_MULTISHOT)

#define ALL_FSNOTIFY_BITS   (ALL_FSNOTIFY_EVENTS | ALL_FSNOTIFY_FLAGS)

struct fsnotify_group;
struct fsnotify_event;
struct fsnotify_mark;
struct fsnotify_event_private_data;
struct fsnotify_fname;
struct fsnotify_iter_info;

struct mem_cgroup;

/*
 * 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
 * @group:      group to notify
 * @mask:       event type and flags
 * @data:       object that event happened on
 * @data_type:  type of object for fanotify_data_XXX() accessors
 * @dir:        optional directory associated with event -
 *              if @file_name is not NULL, this is the directory that
 *              @file_name is relative to
 * @file_name:  optional file name associated with event
 * @cookie:     inotify rename cookie
 * @iter_info:  array of marks from this group that are interested in the event
 *
 * handle_inode_event - simple variant of handle_event() for groups that only
 *              have inode marks and don't have ignore mask
 * @mark:       mark to notify
 * @mask:       event type and flags
 * @inode:      inode that event happened on
 * @dir:        optional directory associated with event -
 *              if @file_name is not NULL, this is the directory that
 *              @file_name is relative to.
 *              Either @inode or @dir must be non-NULL.
 * @file_name:  optional file name associated with event
 * @cookie:     inotify rename cookie
 *
 * free_group_priv - called when a group refcnt hits 0 to clean up the private union
 * freeing_mark - called when a mark is being destroyed for some reason.  The group
 *              MUST be holding a reference on each mark and that reference must be
 *              dropped in this function.  inotify uses this function to send
 *              userspace messages that marks have been removed.
 */
struct fsnotify_ops {
        int (*handle_event)(struct fsnotify_group *group, u32 mask,
                            const void *data, int data_type, struct inode *dir,
                            const struct qstr *file_name, u32 cookie,
                            struct fsnotify_iter_info *iter_info);
        int (*handle_inode_event)(struct fsnotify_mark *mark, u32 mask,
                            struct inode *inode, struct inode *dir,
                            const struct qstr *file_name, u32 cookie);
        void (*free_group_priv)(struct fsnotify_group *group);
        void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
        void (*free_event)(struct fsnotify_group *group, struct fsnotify_event *event);
        /* called on final put+free to free memory */
        void (*free_mark)(struct fsnotify_mark *mark);
};

/*
 * 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 {
        struct list_head list;
};

/*
 * fsnotify group priorities.
 * Events are sent in order from highest priority to lowest priority.
 */
enum fsnotify_group_prio {
        FSNOTIFY_PRIO_NORMAL = 0,       /* normal notifiers, no permissions */
        FSNOTIFY_PRIO_CONTENT,          /* fanotify permission events */
        FSNOTIFY_PRIO_PRE_CONTENT,      /* fanotify pre-content events */
        __FSNOTIFY_PRIO_NUM
};

/*
 * 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 {
        const struct fsnotify_ops *ops; /* how this group handles things */

        /*
         * 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.
         */
        refcount_t refcnt;              /* things with interest in this group */

        /* needed to send notification to userspace */
        spinlock_t notification_lock;           /* protect the notification_list */
        struct list_head notification_list;     /* list of event_holder this group needs to send to userspace */
        wait_queue_head_t notification_waitq;   /* read() on the notification file blocks on this waitq */
        unsigned int q_len;                     /* events on the queue */
        unsigned int max_events;                /* maximum events allowed on the list */
        enum fsnotify_group_prio priority;      /* priority for sending events */
        bool shutdown;          /* group is being shut down, don't queue more events */

#define FSNOTIFY_GROUP_USER     0x01 /* user allocated group */
#define FSNOTIFY_GROUP_DUPS     0x02 /* allow multiple marks per object */
        int flags;
        unsigned int owner_flags;       /* stored flags of mark_mutex owner */

        /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
        struct mutex mark_mutex;        /* protect marks_list */
        atomic_t user_waits;            /* Number of tasks waiting for user
                                         * response */
        struct list_head marks_list;    /* all inode marks for this group */

        struct fasync_struct *fsn_fa;    /* async notification */

        struct fsnotify_event *overflow_event;  /* Event we queue when the
                                                 * notification list is too
                                                 * full */

        struct mem_cgroup *memcg;       /* memcg to charge allocations */
        struct user_namespace *user_ns; /* user ns where group was created */

        /* groups can define private fields here or use the void *private */
        union {
                void *private;
#ifdef CONFIG_INOTIFY_USER
                struct inotify_group_private_data {
                        spinlock_t      idr_lock;
                        struct idr      idr;
                        struct ucounts *ucounts;
                } inotify_data;
#endif
#ifdef CONFIG_FANOTIFY
                struct fanotify_group_private_data {
                        /* Hash table of events for merge */
                        struct hlist_head *merge_hash;
                        /* allows a group to block waiting for a userspace response */
                        struct list_head access_list;
                        wait_queue_head_t access_waitq;
                        int flags;           /* flags from fanotify_init() */
                        int f_flags; /* event_f_flags from fanotify_init() */
                        struct ucounts *ucounts;
                        mempool_t error_events_pool;
                        /* chained on perm_group_list */
                        struct list_head perm_grp_list;
                } fanotify_data;
#endif /* CONFIG_FANOTIFY */
        };
};

/*
 * These helpers are used to prevent deadlock when reclaiming inodes with
 * evictable marks of the same group that is allocating a new mark.
 */
static inline void fsnotify_group_lock(struct fsnotify_group *group)
{
        mutex_lock(&group->mark_mutex);
        group->owner_flags = memalloc_nofs_save();
}

static inline void fsnotify_group_unlock(struct fsnotify_group *group)
{
        memalloc_nofs_restore(group->owner_flags);
        mutex_unlock(&group->mark_mutex);
}

static inline void fsnotify_group_assert_locked(struct fsnotify_group *group)
{
        WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex));
        WARN_ON_ONCE(!(current->flags & PF_MEMALLOC_NOFS));
}

/* When calling fsnotify tell it if the data is a path or inode */
enum fsnotify_data_type {
        FSNOTIFY_EVENT_NONE,
        FSNOTIFY_EVENT_FILE_RANGE,
        FSNOTIFY_EVENT_PATH,
        FSNOTIFY_EVENT_INODE,
        FSNOTIFY_EVENT_DENTRY,
        FSNOTIFY_EVENT_MNT,
        FSNOTIFY_EVENT_ERROR,
};

struct fs_error_report {
        int error;
        struct inode *inode;
        struct super_block *sb;
};

struct file_range {
        const struct path *path;
        loff_t pos;
        size_t count;
};

static inline const struct path *file_range_path(const struct file_range *range)
{
        return range->path;
}

struct fsnotify_mnt {
        const struct mnt_namespace *ns;
        u64 mnt_id;
};

static inline struct inode *fsnotify_data_inode(const void *data, int data_type)
{
        switch (data_type) {
        case FSNOTIFY_EVENT_INODE:
                return (struct inode *)data;
        case FSNOTIFY_EVENT_DENTRY:
                return d_inode(data);
        case FSNOTIFY_EVENT_PATH:
                return d_inode(((const struct path *)data)->dentry);
        case FSNOTIFY_EVENT_FILE_RANGE:
                return d_inode(file_range_path(data)->dentry);
        case FSNOTIFY_EVENT_ERROR:
                return ((struct fs_error_report *)data)->inode;
        default:
                return NULL;
        }
}

static inline struct dentry *fsnotify_data_dentry(const void *data, int data_type)
{
        switch (data_type) {
        case FSNOTIFY_EVENT_DENTRY:
                /* Non const is needed for dget() */
                return (struct dentry *)data;
        case FSNOTIFY_EVENT_PATH:
                return ((const struct path *)data)->dentry;
        case FSNOTIFY_EVENT_FILE_RANGE:
                return file_range_path(data)->dentry;
        default:
                return NULL;
        }
}

static inline const struct path *fsnotify_data_path(const void *data,
                                                    int data_type)
{
        switch (data_type) {
        case FSNOTIFY_EVENT_PATH:
                return data;
        case FSNOTIFY_EVENT_FILE_RANGE:
                return file_range_path(data);
        default:
                return NULL;
        }
}

static inline struct super_block *fsnotify_data_sb(const void *data,
                                                   int data_type)
{
        switch (data_type) {
        case FSNOTIFY_EVENT_INODE:
                return ((struct inode *)data)->i_sb;
        case FSNOTIFY_EVENT_DENTRY:
                return ((struct dentry *)data)->d_sb;
        case FSNOTIFY_EVENT_PATH:
                return ((const struct path *)data)->dentry->d_sb;
        case FSNOTIFY_EVENT_FILE_RANGE:
                return file_range_path(data)->dentry->d_sb;
        case FSNOTIFY_EVENT_ERROR:
                return ((struct fs_error_report *) data)->sb;
        default:
                return NULL;
        }
}

static inline const struct fsnotify_mnt *fsnotify_data_mnt(const void *data,
                                                           int data_type)
{
        switch (data_type) {
        case FSNOTIFY_EVENT_MNT:
                return data;
        default:
                return NULL;
        }
}

static inline u64 fsnotify_data_mnt_id(const void *data, int data_type)
{
        const struct fsnotify_mnt *mnt_data = fsnotify_data_mnt(data, data_type);

        return mnt_data ? mnt_data->mnt_id : 0;
}

static inline struct fs_error_report *fsnotify_data_error_report(
                                                        const void *data,
                                                        int data_type)
{
        switch (data_type) {
        case FSNOTIFY_EVENT_ERROR:
                return (struct fs_error_report *) data;
        default:
                return NULL;
        }
}

static inline const struct file_range *fsnotify_data_file_range(
                                                        const void *data,
                                                        int data_type)
{
        switch (data_type) {
        case FSNOTIFY_EVENT_FILE_RANGE:
                return (struct file_range *)data;
        default:
                return NULL;
        }
}

/*
 * Index to merged marks iterator array that correlates to a type of watch.
 * The type of watched object can be deduced from the iterator type, but not
 * the other way around, because an event can match different watched objects
 * of the same object type.
 * For example, both parent and child are watching an object of type inode.
 */
enum fsnotify_iter_type {
        FSNOTIFY_ITER_TYPE_INODE,
        FSNOTIFY_ITER_TYPE_VFSMOUNT,
        FSNOTIFY_ITER_TYPE_SB,
        FSNOTIFY_ITER_TYPE_PARENT,
        FSNOTIFY_ITER_TYPE_INODE2,
        FSNOTIFY_ITER_TYPE_MNTNS,
        FSNOTIFY_ITER_TYPE_COUNT
};

/* The type of object that a mark is attached to */
enum fsnotify_obj_type {
        FSNOTIFY_OBJ_TYPE_ANY = -1,
        FSNOTIFY_OBJ_TYPE_INODE,
        FSNOTIFY_OBJ_TYPE_VFSMOUNT,
        FSNOTIFY_OBJ_TYPE_SB,
        FSNOTIFY_OBJ_TYPE_MNTNS,
        FSNOTIFY_OBJ_TYPE_COUNT,
        FSNOTIFY_OBJ_TYPE_DETACHED = FSNOTIFY_OBJ_TYPE_COUNT
};

static inline bool fsnotify_valid_obj_type(unsigned int obj_type)
{
        return (obj_type < FSNOTIFY_OBJ_TYPE_COUNT);
}

struct fsnotify_iter_info {
        struct fsnotify_mark *marks[FSNOTIFY_ITER_TYPE_COUNT];
        struct fsnotify_group *current_group;
        unsigned int report_mask;
        int srcu_idx;
};

static inline bool fsnotify_iter_should_report_type(
                struct fsnotify_iter_info *iter_info, int iter_type)
{
        return (iter_info->report_mask & (1U << iter_type));
}

static inline void fsnotify_iter_set_report_type(
                struct fsnotify_iter_info *iter_info, int iter_type)
{
        iter_info->report_mask |= (1U << iter_type);
}

static inline struct fsnotify_mark *fsnotify_iter_mark(
                struct fsnotify_iter_info *iter_info, int iter_type)
{
        if (fsnotify_iter_should_report_type(iter_info, iter_type))
                return iter_info->marks[iter_type];
        return NULL;
}

static inline int fsnotify_iter_step(struct fsnotify_iter_info *iter, int type,
                                     struct fsnotify_mark **markp)
{
        while (type < FSNOTIFY_ITER_TYPE_COUNT) {
                *markp = fsnotify_iter_mark(iter, type);
                if (*markp)
                        break;
                type++;
        }
        return type;
}

#define FSNOTIFY_ITER_FUNCS(name, NAME) \
static inline struct fsnotify_mark *fsnotify_iter_##name##_mark( \
                struct fsnotify_iter_info *iter_info) \
{ \
        return fsnotify_iter_mark(iter_info, FSNOTIFY_ITER_TYPE_##NAME); \
}

FSNOTIFY_ITER_FUNCS(inode, INODE)
FSNOTIFY_ITER_FUNCS(parent, PARENT)
FSNOTIFY_ITER_FUNCS(vfsmount, VFSMOUNT)
FSNOTIFY_ITER_FUNCS(sb, SB)

#define fsnotify_foreach_iter_type(type) \
        for (type = 0; type < FSNOTIFY_ITER_TYPE_COUNT; type++)
#define fsnotify_foreach_iter_mark_type(iter, mark, type) \
        for (type = 0; \
             type = fsnotify_iter_step(iter, type, &mark), \
             type < FSNOTIFY_ITER_TYPE_COUNT; \
             type++)

/*
 * Inode/vfsmount/sb point to this structure which tracks all marks attached to
 * the inode/vfsmount/sb. The reference to inode/vfsmount/sb is held by this
 * structure. We destroy this structure when there are no more marks attached
 * to it. The structure is protected by fsnotify_mark_srcu.
 */
struct fsnotify_mark_connector {
        spinlock_t lock;
        unsigned char type;     /* Type of object [lock] */
        unsigned char prio;     /* Highest priority group */
#define FSNOTIFY_CONN_FLAG_IS_WATCHED   0x01
#define FSNOTIFY_CONN_FLAG_HAS_IREF     0x02
        unsigned short flags;   /* flags [lock] */
        union {
                /* Object pointer [lock] */
                void *obj;
                /* Used listing heads to free after srcu period expires */
                struct fsnotify_mark_connector *destroy_next;
        };
        struct hlist_head list; /* List of marks */
};

/*
 * Container for per-sb fsnotify state (sb marks and more).
 * Attached lazily on first marked object on the sb and freed when killing sb.
 */
struct fsnotify_sb_info {
        struct fsnotify_mark_connector __rcu *sb_marks;
        /* List of connectors for inode marks */
        struct list_head inode_conn_list;
        spinlock_t list_lock;   /* Lock protecting inode_conn_list */
        /*
         * Number of inode/mount/sb objects that are being watched in this sb.
         * Note that inodes objects are currently double-accounted.
         *
         * The value in watched_objects[prio] is the number of objects that are
         * watched by groups of priority >= prio, so watched_objects[0] is the
         * total number of watched objects in this sb.
         */
        atomic_long_t watched_objects[__FSNOTIFY_PRIO_NUM];
};

static inline struct fsnotify_sb_info *fsnotify_sb_info(struct super_block *sb)
{
#ifdef CONFIG_FSNOTIFY
        return READ_ONCE(sb->s_fsnotify_info);
#else
        return NULL;
#endif
}

static inline atomic_long_t *fsnotify_sb_watched_objects(struct super_block *sb)
{
        return &fsnotify_sb_info(sb)->watched_objects[0];
}

/*
 * A mark is simply an object attached to an in core inode which allows an
 * fsnotify listener to indicate they are either no longer interested in events
 * of a type matching mask or only interested in those events.
 *
 * These are flushed when an inode is evicted from core and may be flushed
 * when the inode is modified (as seen by fsnotify_access).  Some fsnotify
 * users (such as dnotify) will flush these when the open fd is closed and not
 * at inode eviction or modification.
 *
 * Text in brackets is showing the lock(s) protecting modifications of a
 * particular entry. obj_lock means either inode->i_lock or
 * mnt->mnt_root->d_lock depending on the mark type.
 */
struct fsnotify_mark {
        /* Mask this mark is for [mark->lock, group->mark_mutex] */
        __u32 mask;
        /* We hold one for presence in g_list. Also one ref for each 'thing'
         * in kernel that found and may be using this mark. */
        refcount_t refcnt;
        /* Group this mark is for. Set on mark creation, stable until last ref
         * is dropped */
        struct fsnotify_group *group;
        /* List of marks by group->marks_list. Also reused for queueing
         * mark into destroy_list when it's waiting for the end of SRCU period
         * before it can be freed. [group->mark_mutex] */
        struct list_head g_list;
        /* Protects inode / mnt pointers, flags, masks */
        spinlock_t lock;
        /* List of marks for inode / vfsmount [connector->lock, mark ref] */
        struct hlist_node obj_list;
        /* Head of list of marks for an object [mark ref] */
        struct fsnotify_mark_connector *connector;
        /* Events types and flags to ignore [mark->lock, group->mark_mutex] */
        __u32 ignore_mask;
        /* General fsnotify mark flags */
#define FSNOTIFY_MARK_FLAG_ALIVE                0x0001
#define FSNOTIFY_MARK_FLAG_ATTACHED             0x0002
        /* inotify mark flags */
#define FSNOTIFY_MARK_FLAG_EXCL_UNLINK          0x0010
#define FSNOTIFY_MARK_FLAG_IN_ONESHOT           0x0020
        /* fanotify mark flags */
#define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x0100
#define FSNOTIFY_MARK_FLAG_NO_IREF              0x0200
#define FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS     0x0400
#define FSNOTIFY_MARK_FLAG_HAS_FSID             0x0800
#define FSNOTIFY_MARK_FLAG_WEAK_FSID            0x1000
        unsigned int flags;             /* flags [mark->lock] */
};

#ifdef CONFIG_FSNOTIFY

/* called from the vfs helpers */

/* main fsnotify call to send events */
extern int fsnotify(__u32 mask, const void *data, int data_type,
                    struct inode *dir, const struct qstr *name,
                    struct inode *inode, u32 cookie);
extern int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
                           int data_type);
extern void __fsnotify_inode_delete(struct inode *inode);
extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
extern void fsnotify_sb_delete(struct super_block *sb);
extern void __fsnotify_mntns_delete(struct mnt_namespace *mntns);
extern void fsnotify_sb_free(struct super_block *sb);
extern u32 fsnotify_get_cookie(void);
extern void fsnotify_mnt(__u32 mask, struct mnt_namespace *ns, struct vfsmount *mnt);

static inline __u32 fsnotify_parent_needed_mask(__u32 mask)
{
        /* FS_EVENT_ON_CHILD is set on marks that want parent/name info */
        if (!(mask & FS_EVENT_ON_CHILD))
                return 0;
        /*
         * This object might be watched by a mark that cares about parent/name
         * info, does it care about the specific set of events that can be
         * reported with parent/name info?
         */
        return mask & FS_EVENTS_POSS_TO_PARENT;
}

static inline int fsnotify_inode_watches_children(struct inode *inode)
{
        __u32 parent_mask = READ_ONCE(inode->i_fsnotify_mask);

        /* FS_EVENT_ON_CHILD is set if the inode may care */
        if (!(parent_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 parent_mask & FS_EVENTS_POSS_ON_CHILD;
}

/*
 * Update the dentry with a flag indicating the interest of its parent to receive
 * filesystem events when those events happens to this dentry->d_inode.
 */
static inline void fsnotify_update_flags(struct dentry *dentry)
{
        assert_spin_locked(&dentry->d_lock);

        /*
         * Serialisation of setting PARENT_WATCHED on the dentries is provided
         * by d_lock. If inotify_inode_watched changes after we have taken
         * d_lock, the following fsnotify_set_children_dentry_flags call will
         * find our entry, so it will spin until we complete here, and update
         * us with the new state.
         */
        if (fsnotify_inode_watches_children(dentry->d_parent->d_inode))
                dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
        else
                dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
}

/* called from fsnotify listeners, such as fanotify or dnotify */

/* create a new group */
extern struct fsnotify_group *fsnotify_alloc_group(
                                const struct fsnotify_ops *ops,
                                int flags);
/* get reference to a group */
extern void fsnotify_get_group(struct fsnotify_group *group);
/* drop reference on a group from fsnotify_alloc_group */
extern void fsnotify_put_group(struct fsnotify_group *group);
/* group destruction begins, stop queuing new events */
extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);
/* destroy group */
extern void fsnotify_destroy_group(struct fsnotify_group *group);
/* fasync handler function */
extern int fsnotify_fasync(int fd, struct file *file, int on);
/* Free event from memory */
extern void fsnotify_destroy_event(struct fsnotify_group *group,
                                   struct fsnotify_event *event);
/* attach the event to the group notification queue */
extern int fsnotify_insert_event(struct fsnotify_group *group,
                                 struct fsnotify_event *event,
                                 int (*merge)(struct fsnotify_group *,
                                              struct fsnotify_event *),
                                 void (*insert)(struct fsnotify_group *,
                                                struct fsnotify_event *));

static inline int fsnotify_add_event(struct fsnotify_group *group,
                                     struct fsnotify_event *event,
                                     int (*merge)(struct fsnotify_group *,
                                                  struct fsnotify_event *))
{
        return fsnotify_insert_event(group, event, merge, NULL);
}

/* Queue overflow event to a notification group */
static inline void fsnotify_queue_overflow(struct fsnotify_group *group)
{
        fsnotify_add_event(group, group->overflow_event, NULL);
}

static inline bool fsnotify_is_overflow_event(u32 mask)
{
        return mask & FS_Q_OVERFLOW;
}

static inline bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group)
{
        assert_spin_locked(&group->notification_lock);

        return list_empty(&group->notification_list);
}

extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
/* return, but do not dequeue the first event on the notification queue */
extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group);
/* return AND dequeue the first event on the notification queue */
extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);
/* Remove event queued in the notification list */
extern void fsnotify_remove_queued_event(struct fsnotify_group *group,
                                         struct fsnotify_event *event);

/* functions used to manipulate the marks attached to inodes */

/*
 * Canonical "ignore mask" including event flags.
 *
 * Note the subtle semantic difference from the legacy ->ignored_mask.
 * ->ignored_mask traditionally only meant which events should be ignored,
 * while ->ignore_mask also includes flags regarding the type of objects on
 * which events should be ignored.
 */
static inline __u32 fsnotify_ignore_mask(struct fsnotify_mark *mark)
{
        __u32 ignore_mask = mark->ignore_mask;

        /* The event flags in ignore mask take effect */
        if (mark->flags & FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS)
                return ignore_mask;

        /*
         * Legacy behavior:
         * - Always ignore events on dir
         * - Ignore events on child if parent is watching children
         */
        ignore_mask |= FS_ISDIR;
        ignore_mask &= ~FS_EVENT_ON_CHILD;
        ignore_mask |= mark->mask & FS_EVENT_ON_CHILD;

        return ignore_mask;
}

/* Legacy ignored_mask - only event types to ignore */
static inline __u32 fsnotify_ignored_events(struct fsnotify_mark *mark)
{
        return mark->ignore_mask & ALL_FSNOTIFY_EVENTS;
}

/*
 * Check if mask (or ignore mask) should be applied depending if victim is a
 * directory and whether it is reported to a watching parent.
 */
static inline bool fsnotify_mask_applicable(__u32 mask, bool is_dir,
                                            int iter_type)
{
        /* Should mask be applied to a directory? */
        if (is_dir && !(mask & FS_ISDIR))
                return false;

        /* Should mask be applied to a child? */
        if (iter_type == FSNOTIFY_ITER_TYPE_PARENT &&
            !(mask & FS_EVENT_ON_CHILD))
                return false;

        return true;
}

/*
 * Effective ignore mask taking into account if event victim is a
 * directory and whether it is reported to a watching parent.
 */
static inline __u32 fsnotify_effective_ignore_mask(struct fsnotify_mark *mark,
                                                   bool is_dir, int iter_type)
{
        __u32 ignore_mask = fsnotify_ignored_events(mark);

        if (!ignore_mask)
                return 0;

        /* For non-dir and non-child, no need to consult the event flags */
        if (!is_dir && iter_type != FSNOTIFY_ITER_TYPE_PARENT)
                return ignore_mask;

        ignore_mask = fsnotify_ignore_mask(mark);
        if (!fsnotify_mask_applicable(ignore_mask, is_dir, iter_type))
                return 0;

        return ignore_mask & ALL_FSNOTIFY_EVENTS;
}

/* Get mask for calculating object interest taking ignore mask into account */
static inline __u32 fsnotify_calc_mask(struct fsnotify_mark *mark)
{
        __u32 mask = mark->mask;

        if (!fsnotify_ignored_events(mark))
                return mask;

        /* Interest in FS_MODIFY may be needed for clearing ignore mask */
        if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
                mask |= FS_MODIFY;

        /*
         * If mark is interested in ignoring events on children, the object must
         * show interest in those events for fsnotify_parent() to notice it.
         */
        return mask | mark->ignore_mask;
}

/* Get mask of events for a list of marks */
extern __u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn);
/* Calculate mask of events for a list of marks */
extern void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn);
extern void fsnotify_init_mark(struct fsnotify_mark *mark,
                               struct fsnotify_group *group);
/* Find mark belonging to given group in the list of marks */
struct fsnotify_mark *fsnotify_find_mark(void *obj, unsigned int obj_type,
                                         struct fsnotify_group *group);
/* attach the mark to the object */
int fsnotify_add_mark(struct fsnotify_mark *mark, void *obj,
                      unsigned int obj_type, int add_flags);
int fsnotify_add_mark_locked(struct fsnotify_mark *mark, void *obj,
                             unsigned int obj_type, int add_flags);

/* attach the mark to the inode */
static inline int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
                                          struct inode *inode,
                                          int add_flags)
{
        return fsnotify_add_mark(mark, inode, FSNOTIFY_OBJ_TYPE_INODE,
                                 add_flags);
}
static inline int fsnotify_add_inode_mark_locked(struct fsnotify_mark *mark,
                                                 struct inode *inode,
                                                 int add_flags)
{
        return fsnotify_add_mark_locked(mark, inode, FSNOTIFY_OBJ_TYPE_INODE,
                                        add_flags);
}

static inline struct fsnotify_mark *fsnotify_find_inode_mark(
                                                struct inode *inode,
                                                struct fsnotify_group *group)
{
        return fsnotify_find_mark(inode, FSNOTIFY_OBJ_TYPE_INODE, group);
}

/* given a group and a mark, flag mark to be freed when all references are dropped */
extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
                                  struct fsnotify_group *group);
/* detach mark from inode / mount list, group list, drop inode reference */
extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
/* free mark */
extern void fsnotify_free_mark(struct fsnotify_mark *mark);
/* Wait until all marks queued for destruction are destroyed */
extern void fsnotify_wait_marks_destroyed(void);
/* Clear all of the marks of a group attached to a given object type */
extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
                                          unsigned int obj_type);
extern void fsnotify_get_mark(struct fsnotify_mark *mark);
extern void fsnotify_put_mark(struct fsnotify_mark *mark);
extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);

static inline void fsnotify_init_event(struct fsnotify_event *event)
{
        INIT_LIST_HEAD(&event->list);
}
int fsnotify_pre_content(const struct path *path, const loff_t *ppos,
                         size_t count);

#else

static inline int fsnotify_pre_content(const struct path *path,
                                       const loff_t *ppos, size_t count)
{
        return 0;
}

static inline int fsnotify(__u32 mask, const void *data, int data_type,
                           struct inode *dir, const struct qstr *name,
                           struct inode *inode, u32 cookie)
{
        return 0;
}

static inline int __fsnotify_parent(struct dentry *dentry, __u32 mask,
                                  const void *data, int data_type)
{
        return 0;
}

static inline void __fsnotify_inode_delete(struct inode *inode)
{}

static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
{}

static inline void fsnotify_sb_delete(struct super_block *sb)
{}

static inline void __fsnotify_mntns_delete(struct mnt_namespace *mntns)
{}

static inline void fsnotify_sb_free(struct super_block *sb)
{}

static inline void fsnotify_update_flags(struct dentry *dentry)
{}

static inline u32 fsnotify_get_cookie(void)
{
        return 0;
}

static inline void fsnotify_unmount_inodes(struct super_block *sb)
{}

static inline void fsnotify_mnt(__u32 mask, struct mnt_namespace *ns, struct vfsmount *mnt)
{}

#endif  /* CONFIG_FSNOTIFY */

#endif  /* __KERNEL __ */

#endif  /* __LINUX_FSNOTIFY_BACKEND_H */