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nfsd: break out comparator into separate function 

Break out the function that compares the rqstp and checksum against a
reply cache entry. While we're at it, track the efficacy of the checksum
over the NFS data by tracking the cases where we would have incorrectly
matched a DRC entry if we had not tracked it or the length.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Jeff Layton 2013-03-27 10:15:37 -04:00 committed by J. Bruce Fields
parent 0b9ea37f24
commit 9dc56143c2
1 changed files with 35 additions and 11 deletions
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46
fs/nfsd/nfscache.c
View File

@ -23,9 +23,21 @@
static struct hlist_head * cache_hash;
static struct list_head lru_head;
static struct kmem_cache *drc_slab;
static unsigned int num_drc_entries;
/* max number of entries allowed in the cache */
static unsigned int max_drc_entries;
/*
* Stats and other tracking of on the duplicate reply cache. All of these and
* the "rc" fields in nfsdstats are protected by the cache_lock
*/
/* total number of entries */
static unsigned int num_drc_entries;
/* cache misses due only to checksum comparison failures */
static unsigned int payload_misses;
/*
* Calculate the hash index from an XID.
*/
@ -273,6 +285,26 @@ nfsd_cache_csum(struct svc_rqst *rqstp)
return csum;
}
static bool
nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
{
/* Check RPC header info first */
if (rqstp->rq_xid != rp->c_xid || rqstp->rq_proc != rp->c_proc ||
rqstp->rq_prot != rp->c_prot || rqstp->rq_vers != rp->c_vers ||
rqstp->rq_arg.len != rp->c_len ||
!rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) ||
rpc_get_port(svc_addr(rqstp)) != rpc_get_port((struct sockaddr *)&rp->c_addr))
return false;
/* compare checksum of NFS data */
if (csum != rp->c_csum) {
++payload_misses;
return false;
}
return true;
}
/*
* Search the request hash for an entry that matches the given rqstp.
* Must be called with cache_lock held. Returns the found entry or
@ -283,18 +315,10 @@ nfsd_cache_search(struct svc_rqst *rqstp, __wsum csum)
{
struct svc_cacherep *rp;
struct hlist_head *rh;
__be32 xid = rqstp->rq_xid;
u32 proto = rqstp->rq_prot,
vers = rqstp->rq_vers,
proc = rqstp->rq_proc;
rh = &cache_hash[request_hash(xid)];
rh = &cache_hash[request_hash(rqstp->rq_xid)];
hlist_for_each_entry(rp, rh, c_hash) {
if (xid == rp->c_xid && proc == rp->c_proc &&
proto == rp->c_prot && vers == rp->c_vers &&
rqstp->rq_arg.len == rp->c_len && csum == rp->c_csum &&
rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) &&
rpc_get_port(svc_addr(rqstp)) == rpc_get_port((struct sockaddr *)&rp->c_addr))
if (nfsd_cache_match(rqstp, csum, rp))
return rp;
}
return NULL;