fs/nfsd/cache.h

   1 /*
   2  * Request reply cache. This was heavily inspired by the
   3  * implementation in 4.3BSD/4.4BSD.
   4  *
   5  * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
   6  */
   7
   8 #ifndef NFSCACHE_H
   9 #define NFSCACHE_H
  10
  11 #include <linux/sunrpc/svc.h>
  12
  13 /*
  14  * Representation of a reply cache entry.
  15  *
  16  * Note that we use a sockaddr_in6 to hold the address instead of the more
  17  * typical sockaddr_storage. This is for space reasons, since sockaddr_storage
  18  * is much larger than a sockaddr_in6.
  19  */
  20 struct svc_cacherep {
  21         struct list_head        c_lru;
  22
  23         unsigned char           c_state,        /* unused, inprog, done */
  24                                 c_type,         /* status, buffer */
  25                                 c_secure : 1;   /* req came from port < 1024 */
  26         struct sockaddr_in6     c_addr;
  27         __be32                  c_xid;
  28         u32                     c_prot;
  29         u32                     c_proc;
  30         u32                     c_vers;
  31         unsigned int            c_len;
  32         __wsum                  c_csum;
  33         unsigned long           c_timestamp;
  34         union {
  35                 struct kvec     u_vec;
  36                 __be32          u_status;
  37         }                       c_u;
  38 };
  39
  40 #define c_replvec               c_u.u_vec
  41 #define c_replstat              c_u.u_status
  42
  43 /* cache entry states */
  44 enum {
  45         RC_UNUSED,
  46         RC_INPROG,
  47         RC_DONE
  48 };
  49
  50 /* return values */
  51 enum {
  52         RC_DROPIT,
  53         RC_REPLY,
  54         RC_DOIT
  55 };
  56
  57 /*
  58  * Cache types.
  59  * We may want to add more types one day, e.g. for diropres and
  60  * attrstat replies. Using cache entries with fixed length instead
  61  * of buffer pointers may be more efficient.
  62  */
  63 enum {
  64         RC_NOCACHE,
  65         RC_REPLSTAT,
  66         RC_REPLBUFF,
  67 };
  68
  69 /*
  70  * If requests are retransmitted within this interval, they're dropped.
  71  */
  72 #define RC_DELAY                (HZ/5)
  73
  74 /* Cache entries expire after this time period */
  75 #define RC_EXPIRE               (120 * HZ)
  76
  77 /* Checksum this amount of the request */
  78 #define RC_CSUMLEN              (256U)
  79
  80 int     nfsd_reply_cache_init(void);
  81 void    nfsd_reply_cache_shutdown(void);
  82 int     nfsd_cache_lookup(struct svc_rqst *);
  83 void    nfsd_cache_update(struct svc_rqst *, int, __be32 *);
  84 int     nfsd_reply_cache_stats_open(struct inode *, struct file *);
  85
  86 #endif /* NFSCACHE_H */