01a7decf75
Now that we're allowing more DRC entries, it becomes a lot easier to hit problems with XID collisions. In order to mitigate those, calculate a checksum of up to the first 256 bytes of each request coming in and store that in the cache entry, along with the total length of the request. This initially used crc32, but Chuck Lever and Jim Rees pointed out that crc32 is probably more heavyweight than we really need for generating these checksums, and recommended looking at using the same routines that are used to generate checksums for IP packets. On an x86_64 KVM guest measurements with ftrace showed ~800ns to use csum_partial vs ~1750ns for crc32. The difference probably isn't terribly significant, but for now we may as well use csum_partial. Signed-off-by: Jeff Layton <jlayton@redhat.com> Stones-thrown-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
95 lines
2 KiB
C
95 lines
2 KiB
C
/*
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* Request reply cache. This was heavily inspired by the
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* implementation in 4.3BSD/4.4BSD.
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*
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* Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
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*/
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#ifndef NFSCACHE_H
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#define NFSCACHE_H
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#include <linux/sunrpc/svc.h>
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/*
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* Representation of a reply cache entry.
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*
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* Note that we use a sockaddr_in6 to hold the address instead of the more
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* typical sockaddr_storage. This is for space reasons, since sockaddr_storage
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* is much larger than a sockaddr_in6.
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*/
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struct svc_cacherep {
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struct hlist_node c_hash;
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struct list_head c_lru;
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unsigned char c_state, /* unused, inprog, done */
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c_type, /* status, buffer */
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c_secure : 1; /* req came from port < 1024 */
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struct sockaddr_in6 c_addr;
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__be32 c_xid;
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u32 c_prot;
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u32 c_proc;
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u32 c_vers;
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unsigned int c_len;
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__wsum c_csum;
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unsigned long c_timestamp;
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union {
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struct kvec u_vec;
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__be32 u_status;
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} c_u;
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};
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#define c_replvec c_u.u_vec
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#define c_replstat c_u.u_status
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/* cache entry states */
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enum {
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RC_UNUSED,
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RC_INPROG,
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RC_DONE
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};
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/* return values */
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enum {
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RC_DROPIT,
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RC_REPLY,
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RC_DOIT
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};
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/*
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* Cache types.
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* We may want to add more types one day, e.g. for diropres and
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* attrstat replies. Using cache entries with fixed length instead
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* of buffer pointers may be more efficient.
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*/
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enum {
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RC_NOCACHE,
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RC_REPLSTAT,
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RC_REPLBUFF,
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};
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/*
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* If requests are retransmitted within this interval, they're dropped.
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*/
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#define RC_DELAY (HZ/5)
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/* Cache entries expire after this time period */
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#define RC_EXPIRE (120 * HZ)
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/* Checksum this amount of the request */
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#define RC_CSUMLEN (256U)
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int nfsd_reply_cache_init(void);
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void nfsd_reply_cache_shutdown(void);
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int nfsd_cache_lookup(struct svc_rqst *);
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void nfsd_cache_update(struct svc_rqst *, int, __be32 *);
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#ifdef CONFIG_NFSD_V4
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void nfsd4_set_statp(struct svc_rqst *rqstp, __be32 *statp);
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#else /* CONFIG_NFSD_V4 */
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static inline void nfsd4_set_statp(struct svc_rqst *rqstp, __be32 *statp)
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{
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}
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#endif /* CONFIG_NFSD_V4 */
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#endif /* NFSCACHE_H */
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