Quelle watch_queue.h Sprache: C

// SPDX-License-Identifier: GPL-2.0
/* User-mappable watch queue
*
* Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* See Documentation/core-api/watch_queue.rst
*/

#ifndef _LINUX_WATCH_QUEUE_H
#define _LINUX_WATCH_QUEUE_H

#include <uapi/linux/watch_queue.h>
#include <linux/kref.h>
#include <linux/rcupdate.h>

#ifdef CONFIG_WATCH_QUEUE

struct cred;

struct watch_type_filter {
enum watch_notification_type type;
__u32  subtype_filter[1]; /* Bitmask of subtypes to filter on */
__u32  info_filter;  /* Filter on watch_notification::info */
__u32  info_mask;  /* Mask of relevant bits in info_filter */
};

struct watch_filter {
union {
  struct rcu_head rcu;
  /* Bitmask of accepted types */
  DECLARE_BITMAP(type_filter, WATCH_TYPE__NR);
};
u32   nr_filters; /* Number of filters */
struct watch_type_filter filters[] __counted_by(nr_filters);
};

struct watch_queue {
struct rcu_head  rcu;
struct watch_filter __rcu *filter;
struct pipe_inode_info *pipe;  /* Pipe we use as a buffer, NULL if queue closed */
struct hlist_head watches; /* Contributory watches */
struct page  **notes; /* Preallocated notifications */
unsigned long  *notes_bitmap; /* Allocation bitmap for notes */
struct kref  usage;  /* Object usage count */
spinlock_t  lock;
unsigned int  nr_notes; /* Number of notes */
unsigned int  nr_pages; /* Number of pages in notes[] */
};

/*
* Representation of a watch on an object.
*/
struct watch {
union {
  struct rcu_head rcu;
  u32  info_id; /* ID to be OR'd in to info field */
};
struct watch_queue __rcu *queue; /* Queue to post events to */
struct hlist_node queue_node; /* Link in queue->watches */
struct watch_list __rcu *watch_list;
struct hlist_node list_node; /* Link in watch_list->watchers */
const struct cred *cred;  /* Creds of the owner of the watch */
void   *private; /* Private data for the watched object */
u64   id;  /* Internal identifier */
struct kref  usage;  /* Object usage count */
};

/*
* List of watches on an object.
*/
struct watch_list {
struct rcu_head  rcu;
struct hlist_head watchers;
void (*release_watch)(struct watch *);
spinlock_t  lock;
};

extern void __post_watch_notification(struct watch_list *,
          struct watch_notification *,
          const struct cred *,
          u64);
extern struct watch_queue *get_watch_queue(int);
extern void put_watch_queue(struct watch_queue *);
extern void init_watch(struct watch *, struct watch_queue *);
extern int add_watch_to_object(struct watch *, struct watch_list *);
extern int remove_watch_from_object(struct watch_list *, struct watch_queue *, u64, bool);
extern long watch_queue_set_size(struct pipe_inode_info *, unsigned int);
extern long watch_queue_set_filter(struct pipe_inode_info *,
       struct watch_notification_filter __user *);
extern int watch_queue_init(struct pipe_inode_info *);
extern void watch_queue_clear(struct watch_queue *);

static inline void init_watch_list(struct watch_list *wlist,
       void (*release_watch)(struct watch *))
{
INIT_HLIST_HEAD(&wlist->watchers);
spin_lock_init(&wlist->lock);
wlist->release_watch = release_watch;
}

static inline void post_watch_notification(struct watch_list *wlist,
        struct watch_notification *n,
        const struct cred *cred,
        u64 id)
{
if (unlikely(wlist))
  __post_watch_notification(wlist, n, cred, id);
}

static inline void remove_watch_list(struct watch_list *wlist, u64 id)
{
if (wlist) {
  remove_watch_from_object(wlist, NULL, id, true);
  kfree_rcu(wlist, rcu);
}
}

/**
* watch_sizeof - Calculate the information part of the size of a watch record,
* given the structure size.
*/
#define watch_sizeof(STRUCT) (sizeof(STRUCT) << WATCH_INFO_LENGTH__SHIFT)

#else
static inline int watch_queue_init(struct pipe_inode_info *pipe)
{
return -ENOPKG;
}

#endif

#endif /* _LINUX_WATCH_QUEUE_H */

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