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knfsd: Simplify NFS duplicate replay cache 

Simplify the duplicate replay cache by initialising the preallocated
cache entry, so that we can use it as a key for the cache lookup.

Note that the 99.999% case we want to optimise for is still the one
where the lookup fails, and we have to add this entry to the cache,
so preinitialising should not cause a performance penalty.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Trond Myklebust 2018-10-01 10:41:55 -04:00 committed by J. Bruce Fields
parent 3e87da5145
commit 76ecec2119
1 changed files with 46 additions and 52 deletions
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98
fs/nfsd/nfscache.c
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@ -121,7 +121,7 @@ nfsd_cache_hash(__be32 xid)
}
static struct svc_cacherep *
nfsd_reply_cache_alloc(void)
nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum)
{
struct svc_cacherep *rp;
@ -130,6 +130,16 @@ nfsd_reply_cache_alloc(void)
rp->c_state = RC_UNUSED;
rp->c_type = RC_NOCACHE;
INIT_LIST_HEAD(&rp->c_lru);
rp->c_xid = rqstp->rq_xid;
rp->c_proc = rqstp->rq_proc;
memset(&rp->c_addr, 0, sizeof(rp->c_addr));
rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
rp->c_prot = rqstp->rq_prot;
rp->c_vers = rqstp->rq_vers;
rp->c_len = rqstp->rq_arg.len;
rp->c_csum = csum;
}
return rp;
}
@ -141,9 +151,11 @@ nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
drc_mem_usage -= rp->c_replvec.iov_len;
kfree(rp->c_replvec.iov_base);
}
list_del(&rp->c_lru);
atomic_dec(&num_drc_entries);
drc_mem_usage -= sizeof(*rp);
if (rp->c_state != RC_UNUSED) {
list_del(&rp->c_lru);
atomic_dec(&num_drc_entries);
drc_mem_usage -= sizeof(*rp);
}
kmem_cache_free(drc_slab, rp);
}
@ -319,24 +331,23 @@ nfsd_cache_csum(struct svc_rqst *rqstp)
}
static bool
nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
nfsd_cache_match(const struct svc_cacherep *key, const struct svc_cacherep *rp)
{
/* Check RPC XID first */
if (rqstp->rq_xid != rp->c_xid)
if (key->c_xid != rp->c_xid)
return false;
/* compare checksum of NFS data */
if (csum != rp->c_csum) {
if (key->c_csum != rp->c_csum) {
++payload_misses;
return false;
}
/* Other discriminators */
if (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))
if (key->c_proc != rp->c_proc ||
key->c_prot != rp->c_prot ||
key->c_vers != rp->c_vers ||
key->c_len != rp->c_len ||
memcmp(&key->c_addr, &rp->c_addr, sizeof(key->c_addr)) != 0)
return false;
return true;
@ -345,19 +356,18 @@ nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
/*
* Search the request hash for an entry that matches the given rqstp.
* Must be called with cache_lock held. Returns the found entry or
* NULL on failure.
* inserts an empty key on failure.
*/
static struct svc_cacherep *
nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp,
__wsum csum)
nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key)
{
struct svc_cacherep *rp, *ret = NULL;
struct svc_cacherep *rp, *ret = key;
struct list_head *rh = &b->lru_head;
unsigned int entries = 0;
list_for_each_entry(rp, rh, c_lru) {
++entries;
if (nfsd_cache_match(rqstp, csum, rp)) {
if (nfsd_cache_match(key, rp)) {
ret = rp;
break;
}
@ -374,6 +384,7 @@ nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp,
atomic_read(&num_drc_entries));
}
lru_put_end(b, ret);
return ret;
}
@ -389,9 +400,6 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
{
struct svc_cacherep *rp, *found;
__be32 xid = rqstp->rq_xid;
u32 proto = rqstp->rq_prot,
vers = rqstp->rq_vers,
proc = rqstp->rq_proc;
__wsum csum;
u32 hash = nfsd_cache_hash(xid);
struct nfsd_drc_bucket *b = &drc_hashtbl[hash];
@ -410,52 +418,38 @@ nfsd_cache_lookup(struct svc_rqst *rqstp)
* Since the common case is a cache miss followed by an insert,
* preallocate an entry.
*/
rp = nfsd_reply_cache_alloc();
spin_lock(&b->cache_lock);
if (likely(rp)) {
atomic_inc(&num_drc_entries);
drc_mem_usage += sizeof(*rp);
}
/* go ahead and prune the cache */
prune_bucket(b);
found = nfsd_cache_search(b, rqstp, csum);
if (found) {
if (likely(rp))
nfsd_reply_cache_free_locked(rp);
rp = found;
goto found_entry;
}
rp = nfsd_reply_cache_alloc(rqstp, csum);
if (!rp) {
dprintk("nfsd: unable to allocate DRC entry!\n");
goto out;
return rtn;
}
spin_lock(&b->cache_lock);
found = nfsd_cache_insert(b, rp);
if (found != rp) {
nfsd_reply_cache_free_locked(rp);
rp = found;
goto found_entry;
}
nfsdstats.rcmisses++;
rqstp->rq_cacherep = rp;
rp->c_state = RC_INPROG;
rp->c_xid = xid;
rp->c_proc = proc;
rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
rp->c_prot = proto;
rp->c_vers = vers;
rp->c_len = rqstp->rq_arg.len;
rp->c_csum = csum;
lru_put_end(b, rp);
atomic_inc(&num_drc_entries);
drc_mem_usage += sizeof(*rp);
/* go ahead and prune the cache */
prune_bucket(b);
out:
spin_unlock(&b->cache_lock);
return rtn;
found_entry:
nfsdstats.rchits++;
/* We found a matching entry which is either in progress or done. */
lru_put_end(b, rp);
nfsdstats.rchits++;
rtn = RC_DROPIT;
/* Request being processed */
if (rp->c_state == RC_INPROG)
goto out;