linux_kernel/fs/nfsd/cache.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Request reply cache. This was heavily inspired by the
 * implementation in 4.3BSD/4.4BSD.
 *
 * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
 */

#ifndef NFSCACHE_H
#define NFSCACHE_H

#include <linux/sunrpc/svc.h>

/*
 * Representation of a reply cache entry.
 *
 * Note that we use a sockaddr_in6 to hold the address instead of the more
 * typical sockaddr_storage. This is for space reasons, since sockaddr_storage
 * is much larger than a sockaddr_in6.
 */
struct svc_cacherep {
	struct {
		/* Keep often-read xid, csum in the same cache line: */
		__be32			k_xid;
		__wsum			k_csum;
		u32			k_proc;
		u32			k_prot;
		u32			k_vers;
		unsigned int		k_len;
		struct sockaddr_in6	k_addr;
	} c_key;

	struct rb_node		c_node;
	struct list_head	c_lru;
	unsigned char		c_state,	/* unused, inprog, done */
				c_type,		/* status, buffer */
				c_secure : 1;	/* req came from port < 1024 */
	unsigned long		c_timestamp;
	union {
		struct kvec	u_vec;
		__be32		u_status;
	}			c_u;
};

#define c_replvec		c_u.u_vec
#define c_replstat		c_u.u_status

/* cache entry states */
enum {
	RC_UNUSED,
	RC_INPROG,
	RC_DONE
};

/* return values */
enum {
	RC_DROPIT,
	RC_REPLY,
	RC_DOIT
};

/*
 * Cache types.
 * We may want to add more types one day, e.g. for diropres and
 * attrstat replies. Using cache entries with fixed length instead
 * of buffer pointers may be more efficient.
 */
enum {
	RC_NOCACHE,
	RC_REPLSTAT,
	RC_REPLBUFF,
};

/* Cache entries expire after this time period */
#define RC_EXPIRE		(120 * HZ)

/* Checksum this amount of the request */
#define RC_CSUMLEN		(256U)

int	nfsd_reply_cache_init(void);
void	nfsd_reply_cache_shutdown(void);
int	nfsd_cache_lookup(struct svc_rqst *);
void	nfsd_cache_update(struct svc_rqst *, int, __be32 *);
int	nfsd_reply_cache_stats_open(struct inode *, struct file *);

#endif /* NFSCACHE_H */