[Virtio-fs] [PATCH 3/4] virtiofsd: fix lo_destroy() resource leaks

[Stefan Hajnoczi]

Now that lo_destroy() is serialized we can call unref_inode() so that
all inode resources are freed.

Signed-off-by: Stefan Hajnoczi <stefanha at redhat.com>
---
 contrib/virtiofsd/passthrough_ll.c | 43 ++++++++++++++----------------
 1 file changed, 20 insertions(+), 23 deletions(-)

diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthrough_ll.c
index a81c01d0d1..02a5e97326 100644
--- a/contrib/virtiofsd/passthrough_ll.c
+++ b/contrib/virtiofsd/passthrough_ll.c
@@ -1340,28 +1340,6 @@ static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n)
 	}
 }
 
-static int unref_all_inodes_cb(gpointer key, gpointer value,
-			       gpointer user_data)
-{
-	struct lo_inode *inode  = value;
-	struct lo_data *lo = user_data;
-
-	inode->nlookup = 0;
-	lo_map_remove(&lo->ino_map, inode->fuse_ino);
-	close(inode->fd);
-	lo_inode_put(lo, &inode); /* Drop our refcount from lo_do_lookup() */
-
-	return TRUE;
-}
-
-static void unref_all_inodes(struct lo_data *lo)
-{
-	pthread_mutex_lock(&lo->mutex);
-	g_hash_table_foreach_remove(lo->inodes, unref_all_inodes_cb, lo);
-	pthread_mutex_unlock(&lo->mutex);
-
-}
-
 static void lo_forget_one(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup)
 {
 	struct lo_data *lo = lo_data(req);
@@ -2462,6 +2440,18 @@ static void lo_removemapping(fuse_req_t req, struct fuse_session *se,
 	fuse_reply_err(req, ret);
 }
 
+static int destroy_inode_cb(gpointer key, gpointer value, gpointer user_data)
+{
+        struct lo_inode *inode = value;
+        struct lo_data *lo = user_data;
+
+        /* inode->nlookup is normally protected by lo->mutex but see the
+         * comment in lo_destroy().
+         */
+        unref_inode(lo, inode, inode->nlookup);
+        return TRUE;
+}
+
 static void lo_destroy(void *userdata, struct fuse_session *se)
 {
 	struct lo_data *lo = (struct lo_data*) userdata;
@@ -2475,7 +2465,14 @@ static void lo_destroy(void *userdata, struct fuse_session *se)
                         fuse_err("%s: unmap during destroy failed\n", __func__);
                 }
         }
-	unref_all_inodes(lo);
+
+        /* Normally lo->mutex must be taken when traversing lo->inodes but
+         * lo_destroy() is a serialized request so no races are possible here.
+         *
+         * In addition, we cannot acquire lo->mutex since destroy_inode_cb() takes it
+         * too and this would result in a recursive lock.
+         */
+        g_hash_table_foreach_remove(lo->inodes, destroy_inode_cb, lo);
 }
 
 static struct fuse_lowlevel_ops lo_oper = {
-- 
2.21.0