From 0b175b18648ebedfe255b11a7792f1d76848a8f7 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Sat, 2 May 2020 11:34:40 -0400 Subject: [PATCH] NFSD: Add tracepoints to NFSD's duplicate reply cache Try to capture DRC failures. Two additional clean-ups: - Introduce Doxygen-style comments for the main entry points - Remove a dprintk that fires for an allocation failure. This was the only dprintk in the REPCACHE class. Reported-by: kbuild test robot [ cel: force typecast for display of checksum values ] Signed-off-by: Chuck Lever --- fs/nfsd/nfscache.c | 57 +++++++++++++++++++++++++++----------------- fs/nfsd/trace.h | 59 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 94 insertions(+), 22 deletions(-) diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c index 96352ab7bd81..945d2f5e760e 100644 --- a/fs/nfsd/nfscache.c +++ b/fs/nfsd/nfscache.c @@ -20,8 +20,7 @@ #include "nfsd.h" #include "cache.h" - -#define NFSDDBG_FACILITY NFSDDBG_REPCACHE +#include "trace.h" /* * We use this value to determine the number of hash buckets from the max @@ -323,8 +322,10 @@ nfsd_cache_key_cmp(const struct svc_cacherep *key, const struct svc_cacherep *rp, struct nfsd_net *nn) { if (key->c_key.k_xid == rp->c_key.k_xid && - key->c_key.k_csum != rp->c_key.k_csum) + key->c_key.k_csum != rp->c_key.k_csum) { ++nn->payload_misses; + trace_nfsd_drc_mismatch(nn, key, rp); + } return memcmp(&key->c_key, &rp->c_key, sizeof(key->c_key)); } @@ -377,15 +378,22 @@ out: return ret; } -/* +/** + * nfsd_cache_lookup - Find an entry in the duplicate reply cache + * @rqstp: Incoming Call to find + * * Try to find an entry matching the current call in the cache. When none * is found, we try to grab the oldest expired entry off the LRU list. If * a suitable one isn't there, then drop the cache_lock and allocate a * new one, then search again in case one got inserted while this thread * didn't hold the lock. + * + * Return values: + * %RC_DOIT: Process the request normally + * %RC_REPLY: Reply from cache + * %RC_DROPIT: Do not process the request further */ -int -nfsd_cache_lookup(struct svc_rqst *rqstp) +int nfsd_cache_lookup(struct svc_rqst *rqstp) { struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id); struct svc_cacherep *rp, *found; @@ -399,7 +407,7 @@ nfsd_cache_lookup(struct svc_rqst *rqstp) rqstp->rq_cacherep = NULL; if (type == RC_NOCACHE) { nfsdstats.rcnocache++; - return rtn; + goto out; } csum = nfsd_cache_csum(rqstp); @@ -409,10 +417,8 @@ nfsd_cache_lookup(struct svc_rqst *rqstp) * preallocate an entry. */ rp = nfsd_reply_cache_alloc(rqstp, csum, nn); - if (!rp) { - dprintk("nfsd: unable to allocate DRC entry!\n"); - return rtn; - } + if (!rp) + goto out; spin_lock(&b->cache_lock); found = nfsd_cache_insert(b, rp, nn); @@ -431,8 +437,10 @@ nfsd_cache_lookup(struct svc_rqst *rqstp) /* go ahead and prune the cache */ prune_bucket(b, nn); - out: + +out_unlock: spin_unlock(&b->cache_lock); +out: return rtn; found_entry: @@ -442,13 +450,13 @@ found_entry: /* Request being processed */ if (rp->c_state == RC_INPROG) - goto out; + goto out_trace; /* From the hall of fame of impractical attacks: * Is this a user who tries to snoop on the cache? */ rtn = RC_DOIT; if (!test_bit(RQ_SECURE, &rqstp->rq_flags) && rp->c_secure) - goto out; + goto out_trace; /* Compose RPC reply header */ switch (rp->c_type) { @@ -460,7 +468,7 @@ found_entry: break; case RC_REPLBUFF: if (!nfsd_cache_append(rqstp, &rp->c_replvec)) - goto out; /* should not happen */ + goto out_unlock; /* should not happen */ rtn = RC_REPLY; break; default: @@ -468,13 +476,19 @@ found_entry: nfsd_reply_cache_free_locked(b, rp, nn); } - goto out; +out_trace: + trace_nfsd_drc_found(nn, rqstp, rtn); + goto out_unlock; } -/* - * Update a cache entry. This is called from nfsd_dispatch when - * the procedure has been executed and the complete reply is in - * rqstp->rq_res. +/** + * nfsd_cache_update - Update an entry in the duplicate reply cache. + * @rqstp: svc_rqst with a finished Reply + * @cachetype: which cache to update + * @statp: Reply's status code + * + * This is called from nfsd_dispatch when the procedure has been + * executed and the complete reply is in rqstp->rq_res. * * We're copying around data here rather than swapping buffers because * the toplevel loop requires max-sized buffers, which would be a waste @@ -487,8 +501,7 @@ found_entry: * nfsd failed to encode a reply that otherwise would have been cached. * In this case, nfsd_cache_update is called with statp == NULL. */ -void -nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp) +void nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp) { struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id); struct svc_cacherep *rp = rqstp->rq_cacherep; diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h index 78c574251c60..371dc198d28e 100644 --- a/fs/nfsd/trace.h +++ b/fs/nfsd/trace.h @@ -432,6 +432,65 @@ TRACE_EVENT(nfsd_file_fsnotify_handle_event, __entry->nlink, __entry->mode, __entry->mask) ); +#include "cache.h" + +TRACE_DEFINE_ENUM(RC_DROPIT); +TRACE_DEFINE_ENUM(RC_REPLY); +TRACE_DEFINE_ENUM(RC_DOIT); + +#define show_drc_retval(x) \ + __print_symbolic(x, \ + { RC_DROPIT, "DROPIT" }, \ + { RC_REPLY, "REPLY" }, \ + { RC_DOIT, "DOIT" }) + +TRACE_EVENT(nfsd_drc_found, + TP_PROTO( + const struct nfsd_net *nn, + const struct svc_rqst *rqstp, + int result + ), + TP_ARGS(nn, rqstp, result), + TP_STRUCT__entry( + __field(unsigned long long, boot_time) + __field(unsigned long, result) + __field(u32, xid) + ), + TP_fast_assign( + __entry->boot_time = nn->boot_time; + __entry->result = result; + __entry->xid = be32_to_cpu(rqstp->rq_xid); + ), + TP_printk("boot_time=%16llx xid=0x%08x result=%s", + __entry->boot_time, __entry->xid, + show_drc_retval(__entry->result)) + +); + +TRACE_EVENT(nfsd_drc_mismatch, + TP_PROTO( + const struct nfsd_net *nn, + const struct svc_cacherep *key, + const struct svc_cacherep *rp + ), + TP_ARGS(nn, key, rp), + TP_STRUCT__entry( + __field(unsigned long long, boot_time) + __field(u32, xid) + __field(u32, cached) + __field(u32, ingress) + ), + TP_fast_assign( + __entry->boot_time = nn->boot_time; + __entry->xid = be32_to_cpu(key->c_key.k_xid); + __entry->cached = (__force u32)key->c_key.k_csum; + __entry->ingress = (__force u32)rp->c_key.k_csum; + ), + TP_printk("boot_time=%16llx xid=0x%08x cached-csum=0x%08x ingress-csum=0x%08x", + __entry->boot_time, __entry->xid, __entry->cached, + __entry->ingress) +); + #endif /* _NFSD_TRACE_H */ #undef TRACE_INCLUDE_PATH