smb: client: remove unused fid_lock

The fid_lock in struct cached_fid does not currently provide any real
synchronization. Previously, it had the intention to prevent a double
release of the dentry, but every change to cfid->dentry is already
protected either by cfid_list_lock (while the entry is in the list) or
happens after the cfid has been removed (so no other thread should find
it).

Since there is no scenario in which fid_lock prevents any race, it is
vestigial and can be removed along with its associated
spin_lock()/spin_unlock() calls.

Signed-off-by: Henrique Carvalho <henrique.carvalho@suse.com>
Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: hac-v

fs/smb/client/cached_dir.c

@@ -524,10 +524,9 @@ void close_all_cached_dirs(struct cifs_sb_info *cifs_sb)
 				spin_unlock(&cifs_sb->tlink_tree_lock);
 				goto done;
 			}
-			spin_lock(&cfid->fid_lock);
+
 			tmp_list->dentry = cfid->dentry;
 			cfid->dentry = NULL;
-			spin_unlock(&cfid->fid_lock);
 
 			list_add_tail(&tmp_list->entry, &entry);
 		}
@@ -610,14 +609,9 @@ static void cached_dir_put_work(struct work_struct *work)
 {
 	struct cached_fid *cfid = container_of(work, struct cached_fid,
 					       put_work);
-	struct dentry *dentry;
-
-	spin_lock(&cfid->fid_lock);
-	dentry = cfid->dentry;
+	dput(cfid->dentry);
 	cfid->dentry = NULL;
-	spin_unlock(&cfid->fid_lock);
 
-	dput(dentry);
 	queue_work(serverclose_wq, &cfid->close_work);
 }
 
@@ -675,7 +669,6 @@ static struct cached_fid *init_cached_dir(const char *path)
 	INIT_LIST_HEAD(&cfid->entry);
 	INIT_LIST_HEAD(&cfid->dirents.entries);
 	mutex_init(&cfid->dirents.de_mutex);
-	spin_lock_init(&cfid->fid_lock);
 	kref_init(&cfid->refcount);
 	return cfid;
 }
@@ -742,7 +735,6 @@ static void cfids_laundromat_worker(struct work_struct *work)
 {
 	struct cached_fids *cfids;
 	struct cached_fid *cfid, *q;
-	struct dentry *dentry;
 	LIST_HEAD(entry);
 
 	cfids = container_of(work, struct cached_fids, laundromat_work.work);
@@ -769,12 +761,9 @@ static void cfids_laundromat_worker(struct work_struct *work)
 	list_for_each_entry_safe(cfid, q, &entry, entry) {
 		list_del(&cfid->entry);
 
-		spin_lock(&cfid->fid_lock);
-		dentry = cfid->dentry;
+		dput(cfid->dentry);
 		cfid->dentry = NULL;
-		spin_unlock(&cfid->fid_lock);
 
-		dput(dentry);
 		if (cfid->is_open) {
 			spin_lock(&cifs_tcp_ses_lock);
 			++cfid->tcon->tc_count;

fs/smb/client/cached_dir.h

@@ -44,7 +44,6 @@ struct cached_fid {
 	unsigned long last_access_time; /* jiffies of when last accessed */
 	struct kref refcount;
 	struct cifs_fid fid;
-	spinlock_t fid_lock;
 	struct cifs_tcon *tcon;
 	struct dentry *dentry;
 	struct work_struct put_work;