NFSD: Trace filecache LRU activity

Observe the operation of garbage collection and the lifetime of
filecache items.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 31 insertions, 13 deletions

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index f58685f1b120..e831a7b4f916 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -261,6 +261,18 @@ nfsd_file_flush(struct nfsd_file *nf)
 		nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id));
 }
 
+static void nfsd_file_lru_add(struct nfsd_file *nf)
+{
+	if (list_lru_add(&nfsd_file_lru, &nf->nf_lru))
+		trace_nfsd_file_lru_add(nf);
+}
+
+static void nfsd_file_lru_remove(struct nfsd_file *nf)
+{
+	if (list_lru_del(&nfsd_file_lru, &nf->nf_lru))
+		trace_nfsd_file_lru_del(nf);
+}
+
 static void
 nfsd_file_do_unhash(struct nfsd_file *nf)
 {
@@ -280,8 +292,7 @@ nfsd_file_unhash(struct nfsd_file *nf)
 {
 	if (test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
 		nfsd_file_do_unhash(nf);
-		if (!list_empty(&nf->nf_lru))
-			list_lru_del(&nfsd_file_lru, &nf->nf_lru);
+		nfsd_file_lru_remove(nf);
 		return true;
 	}
 	return false;
@@ -444,27 +455,34 @@ nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru,
 	 * counter. Here we check the counter and then test and clear the flag.
 	 * That order is deliberate to ensure that we can do this locklessly.
 	 */
-	if (refcount_read(&nf->nf_ref) > 1)
-		goto out_skip;
+	if (refcount_read(&nf->nf_ref) > 1) {
+		trace_nfsd_file_gc_in_use(nf);
+		return LRU_SKIP;
+	}
 
 	/*
 	 * Don't throw out files that are still undergoing I/O or
 	 * that have uncleared errors pending.
 	 */
-	if (nfsd_file_check_writeback(nf))
-		goto out_skip;
+	if (nfsd_file_check_writeback(nf)) {
+		trace_nfsd_file_gc_writeback(nf);
+		return LRU_SKIP;
+	}
 
-	if (test_and_clear_bit(NFSD_FILE_REFERENCED, &nf->nf_flags))
-		goto out_skip;
+	if (test_and_clear_bit(NFSD_FILE_REFERENCED, &nf->nf_flags)) {
+		trace_nfsd_file_gc_referenced(nf);
+		return LRU_SKIP;
+	}
 
-	if (!test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags))
-		goto out_skip;
+	if (!test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
+		trace_nfsd_file_gc_hashed(nf);
+		return LRU_SKIP;
+	}
 
 	list_lru_isolate_move(lru, &nf->nf_lru, head);
 	this_cpu_inc(nfsd_file_evictions);
+	trace_nfsd_file_gc_disposed(nf);
 	return LRU_REMOVED;
-out_skip:
-	return LRU_SKIP;
 }
 
 /*
@@ -1017,7 +1035,7 @@ open_file:
 	refcount_inc(&nf->nf_ref);
 	__set_bit(NFSD_FILE_HASHED, &nf->nf_flags);
 	__set_bit(NFSD_FILE_PENDING, &nf->nf_flags);
-	list_lru_add(&nfsd_file_lru, &nf->nf_lru);
+	nfsd_file_lru_add(nf);
 	hlist_add_head_rcu(&nf->nf_node, &nfsd_file_hashtbl[hashval].nfb_head);
 	++nfsd_file_hashtbl[hashval].nfb_count;
 	nfsd_file_hashtbl[hashval].nfb_maxcount = max(nfsd_file_hashtbl[hashval].nfb_maxcount,