In my program, I need to generate dynamic number and dynamic size of textures.So I write a function to do this

int TexGener::genTex(const ivec2& texSize,int layer){
    if(curContext->makeCurrent(this)){
        GLuint tmpTbo = 0;
        func->glActiveTexture(GL_TEXTURE5);
        func->glGenTextures(1,&tmpTbo);
        func->glBindTexture(GL_TEXTURE_2D,tmpTbo);
        int wid = texSize.x;
        int hei = texSize.y;
        func->glTexStorage2D(GL_TEXTURE_2D,layer,GL_RGBA16F,wid,hei);
        if(layer == 1){
            func->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
            func->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
            func->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
            func->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
        }
        else{
            func->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);//use mipmap
            func->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
            func->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
            func->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        }
        GLint result;
        func->glGetTexParameteriv(GL_TEXTURE_2D,GL_TEXTURE_IMMUTABLE_FORMAT,&result);
        qDebug()<<"texture malloc:"<<result;
        curContext->doneCurrent();
        if(tmpTbo > 0){
            appliedTex.append(tmpTbo);
            return appliedTex.size() - 1;
        }
    }
    return -1;
}

In this function,texSize specifies the width and height of a texture, layer specifies the levels.I find that if texSize is bigger than 2048 * 2048,glTexStorage2D could fail sometimes,but always success if smaller than 2048* 2048. Then I checked GPU memory, only 500MB which is 8% of whole 6GB GPU memory is occupied when calling this funcion,I don’t know why could glTexStorage2D fail,and how can I fix this?