Re: [PATCH 102/104] virtiofsd: fix lo_destroy() resource leaks

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 12/12/19 5:39 PM, Dr. David Alan Gilbert (git) wrote:
> From: Stefan Hajnoczi <stefanha@redhat.com>
> 
> Now that lo_destroy() is serialized we can call unref_inode() so that
> all inode resources are freed.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>   tools/virtiofsd/passthrough_ll.c | 41 ++++++++++++++++----------------
>   1 file changed, 20 insertions(+), 21 deletions(-)
> 
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index 1bf251a91d..38f4948e61 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -1355,26 +1355,6 @@ static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode,
>       }
>   }
>   
> -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);
> @@ -2460,7 +2440,26 @@ static void lo_lseek(fuse_req_t req, fuse_ino_t ino, off_t off, int whence,
>   static void lo_destroy(void *userdata)
>   {
>       struct lo_data *lo = (struct lo_data *)userdata;
> -    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 unref_inode() takes it
> +     * too and this would result in a recursive lock.
> +     */
> +    while (true) {
> +        GHashTableIter iter;
> +        gpointer key, value;
> +
> +        g_hash_table_iter_init(&iter, lo->inodes);
> +        if (!g_hash_table_iter_next(&iter, &key, &value)) {
> +            break;
> +        }
> +
> +        struct lo_inode *inode = value;
> +        unref_inode_lolocked(lo, inode, inode->nlookup);
> +    }
>   }
>   
>   static struct fuse_lowlevel_ops lo_oper = {
> 

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>