nfsd: convert file cache to use over/underflow safe refcount

Use the 'refcount_t' type instead of 'atomic_t' for improved
refcounting safety.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/filecache.c

@@ -100,7 +100,7 @@ nfsd_file_mark_free(struct fsnotify_mark *mark)
 static struct nfsd_file_mark *
 nfsd_file_mark_get(struct nfsd_file_mark *nfm)
 {
-	if (!atomic_inc_not_zero(&nfm->nfm_ref))
+	if (!refcount_inc_not_zero(&nfm->nfm_ref))
 		return NULL;
 	return nfm;
 }
@@ -108,8 +108,7 @@ nfsd_file_mark_get(struct nfsd_file_mark *nfm)
 static void
 nfsd_file_mark_put(struct nfsd_file_mark *nfm)
 {
-	if (atomic_dec_and_test(&nfm->nfm_ref)) {
-
+	if (refcount_dec_and_test(&nfm->nfm_ref)) {
 		fsnotify_destroy_mark(&nfm->nfm_mark, nfsd_file_fsnotify_group);
 		fsnotify_put_mark(&nfm->nfm_mark);
 	}
@@ -148,7 +147,7 @@ nfsd_file_mark_find_or_create(struct nfsd_file *nf)
 			return NULL;
 		fsnotify_init_mark(&new->nfm_mark, nfsd_file_fsnotify_group);
 		new->nfm_mark.mask = FS_ATTRIB|FS_DELETE_SELF;
-		atomic_set(&new->nfm_ref, 1);
+		refcount_set(&new->nfm_ref, 1);
 
 		err = fsnotify_add_inode_mark(&new->nfm_mark, inode, 0);
 
@@ -186,7 +185,7 @@ nfsd_file_alloc(struct inode *inode, unsigned int may, unsigned int hashval,
 		nf->nf_flags = 0;
 		nf->nf_inode = inode;
 		nf->nf_hashval = hashval;
-		atomic_set(&nf->nf_ref, 1);
+		refcount_set(&nf->nf_ref, 1);
 		nf->nf_may = may & NFSD_FILE_MAY_MASK;
 		if (may & NFSD_MAY_NOT_BREAK_LEASE) {
 			if (may & NFSD_MAY_WRITE)
@@ -280,7 +279,7 @@ nfsd_file_unhash_and_release_locked(struct nfsd_file *nf, struct list_head *disp
 	if (!nfsd_file_unhash(nf))
 		return false;
 	/* keep final reference for nfsd_file_lru_dispose */
-	if (atomic_add_unless(&nf->nf_ref, -1, 1))
+	if (refcount_dec_not_one(&nf->nf_ref))
 		return true;
 
 	list_add(&nf->nf_lru, dispose);
@@ -292,7 +291,7 @@ nfsd_file_put_noref(struct nfsd_file *nf)
 {
 	trace_nfsd_file_put(nf);
 
-	if (atomic_dec_and_test(&nf->nf_ref)) {
+	if (refcount_dec_and_test(&nf->nf_ref)) {
 		WARN_ON(test_bit(NFSD_FILE_HASHED, &nf->nf_flags));
 		nfsd_file_free(nf);
 	}
@@ -304,7 +303,7 @@ nfsd_file_put(struct nfsd_file *nf)
 	bool is_hashed;
 
 	set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags);
-	if (atomic_read(&nf->nf_ref) > 2 || !nf->nf_file) {
+	if (refcount_read(&nf->nf_ref) > 2 || !nf->nf_file) {
 		nfsd_file_put_noref(nf);
 		return;
 	}
@@ -321,7 +320,7 @@ nfsd_file_put(struct nfsd_file *nf)
 struct nfsd_file *
 nfsd_file_get(struct nfsd_file *nf)
 {
-	if (likely(atomic_inc_not_zero(&nf->nf_ref)))
+	if (likely(refcount_inc_not_zero(&nf->nf_ref)))
 		return nf;
 	return NULL;
 }
@@ -347,7 +346,7 @@ nfsd_file_dispose_list_sync(struct list_head *dispose)
 	while(!list_empty(dispose)) {
 		nf = list_first_entry(dispose, struct nfsd_file, nf_lru);
 		list_del(&nf->nf_lru);
-		if (!atomic_dec_and_test(&nf->nf_ref))
+		if (!refcount_dec_and_test(&nf->nf_ref))
 			continue;
 		if (nfsd_file_free(nf))
 			flush = true;
@@ -430,7 +429,7 @@ 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 (atomic_read(&nf->nf_ref) > 1)
+	if (refcount_read(&nf->nf_ref) > 1)
 		goto out_skip;
 
 	/*
@@ -1019,7 +1018,7 @@ nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
 open_file:
 	nf = new;
 	/* Take reference for the hashtable */
-	atomic_inc(&nf->nf_ref);
+	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);

fs/nfsd/filecache.h

@@ -19,7 +19,7 @@
  */
 struct nfsd_file_mark {
 	struct fsnotify_mark	nfm_mark;
-	atomic_t		nfm_ref;
+	refcount_t		nfm_ref;
 };
 
 /*
@@ -43,7 +43,7 @@ struct nfsd_file {
 	unsigned long		nf_flags;
 	struct inode		*nf_inode;
 	unsigned int		nf_hashval;
-	atomic_t		nf_ref;
+	refcount_t		nf_ref;
 	unsigned char		nf_may;
 	struct nfsd_file_mark	*nf_mark;
 	struct rw_semaphore	nf_rwsem;

fs/nfsd/trace.h

@@ -201,7 +201,7 @@ DECLARE_EVENT_CLASS(nfsd_file_class,
 	TP_fast_assign(
 		__entry->nf_hashval = nf->nf_hashval;
 		__entry->nf_inode = nf->nf_inode;
-		__entry->nf_ref = atomic_read(&nf->nf_ref);
+		__entry->nf_ref = refcount_read(&nf->nf_ref);
 		__entry->nf_flags = nf->nf_flags;
 		__entry->nf_may = nf->nf_may;
 		__entry->nf_file = nf->nf_file;
@@ -250,7 +250,7 @@ TRACE_EVENT(nfsd_file_acquire,
 		__entry->hash = hash;
 		__entry->inode = inode;
 		__entry->may_flags = may_flags;
-		__entry->nf_ref = nf ? atomic_read(&nf->nf_ref) : 0;
+		__entry->nf_ref = nf ? refcount_read(&nf->nf_ref) : 0;
 		__entry->nf_flags = nf ? nf->nf_flags : 0;
 		__entry->nf_may = nf ? nf->nf_may : 0;
 		__entry->nf_file = nf ? nf->nf_file : NULL;